


















                                  P C - E C A P

                                   Version 3.02




                             Program Reference Manual


                      Copyright (c) 1990-98 by Peter Volpa
                               All Rights Reserved












                              _______
                         ____|__     |                (R)
                      --|       |    |-------------------
                        |   ____|__  |  Association of
                        |  |       |_|  Shareware
                        |__|   o   |    Professionals
                      -----|   |   |---------------------
                           |___|___|    MEMBER



                                   Peter Volpa
                                 Circuit Systems
                                 281 Middle Road
                            Hammonton, NJ 08037-8988  USA






                                Table of Contents
                                -----------------



          Introduction . . . . . . . . . . . . . . . . . . . . .  1
              License  . . . . . . . . . . . . . . . . . . . . .  2
              Ordering Information . . . . . . . . . . . . . . .  3
                (also registering by credit card)
              Disclaimer, Trademarks, ASP info . . . . . . . . .  4
              System Requirements  . . . . . . . . . . . . . . .  5
              Installing PC-ECAP . . . . . . . . . . . . . . . .  6

          Quick Start  . . . . . . . . . . . . . . . . . . . . .  7

          Miscellaneous program information :
              Printer configuration  . . . . . . . . . . . . . .  8
              Data format  . . . . . . . . . . . . . . . . . . .  9
              Accessing data files in other directories  . . . .  9
              Memory requirements vs. maximum circuit nodes  . .  9
              Network / Multi-User operation . . . . . . . . . .  10

          Getting Started  . . . . . . . . . . . . . . . . . . .  11
          Main Menu Descriptions . . . . . . . . . . . . . . . .  11
              Select input file  . . . . . . . . . . . . . . . .  11
              Edit input file  . . . . . . . . . . . . . . . . .  12
              Analyze circuit  . . . . . . . . . . . . . . . . .  16
                Plotting results . . . . . . . . . . . . . . . .  17
              View output data . . . . . . . . . . . . . . . . .  18
              Output to printer  . . . . . . . . . . . . . . . .  18
              Change program settings  . . . . . . . . . . . . .  19
                (number of sample points, printer type, etc.)
              Quit this program  . . . . . . . . . . . . . . . .  20

          Analyzing a Circuit Using PC-ECAP  . . . . . . . . . .  21
              Input format . . . . . . . . . . . . . . . . . . .  22
              Circuit element description  . . . . . . . . . . .  23
              Specifying AC analysis parameters  . . . . . . . .  26
                (group delay, impedance, vswr, return loss)
              Specifying transient analysis parameters . . . . .  28
              Computational techniques for transient analysis  .  30
              An example!  . . . . . . . . . . . . . . . . . . .  33
              An example of transient analysis . . . . . . . . .  34
              Another example (using the Model Maker)  . . . . .  36

          Models . . . . . . . . . . . . . . . . . . . . . . . .  38
              References for modeling  . . . . . . . . . . . . .  39

          Revision History . . . . . . . . . . . . . . . . . . .  40

          Appendix A - Command Line Switches . . . . . . . . . .  42
          Appendix B - Error Messages  . . . . . . . . . . . . .  43
          Appendix C - PC-ECAP to Lotus 1-2-3 file conversion  .  48
          PC-ECAP Reference Manual                          page 1

          Introduction

          PC-ECAP is an easy to use AC circuit analysis program which
          analyzes circuits consisting of resistors, capacitors,
          inductors, transformers, transmission lines, transistors
          (both bipolar and FET's), operational amplifiers and
          transconductance amplifiers.

          Totally integrated in one package, it contains a full screen
          text editor for preparing analysis input, an electronic
          circuit analyzer that calculates your circuit's frequency
          and transient response, a high resolution display plotter
          that supports all common graphics adapters and a high
          resolution plotter compatible with most printers.


          Features:

               *    Calculates Magnitude, Phase, Group Delay,
                    Impedance, VSWR and Return Loss.

               *    Calculates Transient response for step, pulse,
                    ramp, square wave, triangle wave and sine wave
                    inputs.  Can also calculate impulse response.

               *    Completely menu driven - very easy to use.

               *    Can analyze circuits with up to 90 nodes,
                    and with as many as 1000 components.

               *    Built in full screen editor with on-line help
                    function.

               *    Free input format - common abbreviations such as
                    P, U, N, M, K, MEG, G are recognized.  For
                    example if your circuit has a 47pf capacitor, all
                    you need to enter for its value is 47pf.

               *    Supports CGA, EGA, VGA, Hercules, MCGA, AT&T and
                    even the Monochrome Display Adapter.

               *    All calculations are done in 15 digits of double
                    precision.

               *    High resolution plots on IBM/Epson 9 and 24 pin
                    compatible printers, HP LaserJet, and HP DeskJet.

               *    Program may be configured to send its output to
                    LPT1, LPT2, LPT3 or a disk file.

               *    Bipolar transistor model maker.  Just enter your
                    transistor's operating parameters and PC-ECAP will
                    create a Hybrid-Pi model for your transistor.

               *    Will utilize a math coprocessor if available, but
                    does NOT require one.

               *    Built-in network / multi-user support.
          PC-ECAP Reference Manual                          page 2

          License

          PC-ECAP is distributed as Shareware.  It is NOT public
          domain or free software.

          Non-registered users of this software are given the
          opportunity to evaluate the complete PC-ECAP software
          package for 30 days with no obligation.  If, after the
          evaluation period, you find PC-ECAP to be suitable for your
          needs, you must register your copy or discontinue using
          PC-ECAP.

          What we're saying is if you use this program, then you
          should pay for your copy.  That way Circuit Systems will be
          able to provide updates, support, and generally stay in
          business.

          PC-ECAP is distributed in two forms: a registered version
          and an unregistered version.  The unregistered version is a
          fully-functional program that has all the features of the
          registered version.  However, the unregistered version
          requires the user to go through an initialization procedure
          each time PC-ECAP is started.  The initialization procedure
          requires the user to enter a random number before PC-ECAP
          will run.  The registered version does not have this
          initialization procedure.

          The REGISTERED version of PC-ECAP is LICENSED TO THE SINGLE
          PERSON WHO REGISTERED THE PROGRAM AND MAY NOT BE DISTRIBUTED
          IN ANY MANNER.

          All users are granted a limited license to copy the
          UNREGISTERED version of PC-ECAP for the trial use of others.
          This license does NOT include distribution or copying of
          this software:


               *    In conjunction with any other product or service.

               *    In general use within a company or school.

               *    For any "disk fee" other than a small (generally
                    $2.00 to $5.00) copying charge.

               *    For distribution in any modified form.  The file
                    containing this license information MUST be
                    included along with full documentation and all
                    the files that make up this software package.
          PC-ECAP Reference Manual                          page 3

          Ordering Information

          A PC-ECAP registration licenses you to use the product on a
          regular basis.  Registration also entitles you to technical
          support, update notices, and enables you to get future
          releases of PC-ECAP at a minimal price.

          Individual registration costs $69 (plus $2.00 shipping and
          handling).  Upon receipt of your paid registration form, we
          will send you the latest registered version of PC-ECAP with
          documentation on the disk.  New Jersey residents should
          include 6% sales tax.

          Site licensing is also available.  Prices are based on the
          estimated number of users.  Please write for more
          information.

          A PC-ECAP registration form is included in the distribution
          package for your convenience.  It is in the file ORDERFRM.TXT.
          Please take time to fill it out and return it.  If you would
          like high-quality software to continue to be made available
          on a try-first basis and for a reasonable cost, it is up to
          YOU to support such programs.

          Please send your registration form, suggestions and any
          comments that you might have to:

                    Peter Volpa         or       For questions only,
                  Circuit Systems                 no orders.  Call
                  281 Middle Road                  (609) 704-8658
             Hammonton, NJ  08037-8988

          Questions may also be sent by Email to
              `circuitsys@compuserve.com'.

          For the latest product information, please visit our web site:

          http://ourworld.compuserve.com/homepages/circuitsys


          Registering PC-ECAP by Credit Card

          We have established a special arrangement with the Public
          (software) Library for those of you who wish to order by
          credit card.  For credit card orders only, you can order
          from PsL with your Master Card, Visa, AmEx or Discover card
          by calling 800-242-4775 Ext. 10411 or 713-524-6394 Ext. 10411.
          You may also FAX to 713-524-6398 or mail to PsL, P.O. Box 35705,
          Houston, TX 77235-5705.  These numbers are for ordering only.
          For information about volume discounts, site licensing,
          shipping of product, returns, latest version number or other
          technical information, please write to Circuit Systems or
          call 609-704-8658.

          You can also order on-line from our web site:
          http://ourworld.compuserve.com/homepages/circuitsys/pcecap.htm
          just click "Order Online".
          PC-ECAP Reference Manual                          page 4

          DISCLAIMER

          ALTHOUGH WE HAVE EXTENSIVELY TESTED PC-ECAP AND BELIEVE IT
          WILL GIVE ACCURATE RESULTS IF USED CORRECTLY, WE SUPPLY THIS
          PROGRAM AS IS.  CIRCUIT SYSTEMS DISCLAIMS ALL WARRANTIES,
          EXPRESSED OR IMPLIED, THAT THIS PROGRAM IS FIT FOR ANY
          PURPOSE.  CIRCUIT SYSTEMS ALSO ASSUMES NO LIABILITY FOR ANY
          DAMAGES EITHER DIRECT OR CONSEQUENTIAL, WHICH MAY RESULT
          FROM THE USE OF THIS PROGRAM.


          Trademarks

          MS-DOS and Excel are registered trademarks of Microsoft
               Corporation.

          PC-DOS, PC/AT, PC/XT, and PS/2 are registered trademarks of
               IBM Corporation.

          Compaq is a registered trademark of Compaq Computer Corp.

          Hercules is a registered trademark of Hercules Computer
               Technology.

          AT&T is a registered trademark of American Telephone and
               Telegraph Company.

          Olivetti is a registered trademark of Ing. C. Olivetti.

          LaserJet and DeskJet are registered trademarks of
               Hewlett-Packard Company.

          Lotus and 1-2-3 are registered trademarks of Lotus
               Development Corporation.

          Quattro Pro is a registered trademark of Borland
               International Corp.

          AS-EASY-AS is a trademark of TRIUS, Inc.


          Association of Shareware Professionals

          This program is produced by a member of the Association of
          Shareware Professionals (ASP).  ASP wants to make sure that
          the shareware principle works for you. If you are unable to
          resolve a shareware-related problem with an ASP member by
          contacting the member directly, ASP may be able to help. The
          ASP Ombudsman can help you resolve a dispute or problem with
          an ASP member, but does not provide technical support for
          members' products.  Please write to the ASP Ombudsman at
          157-F Love Ave., Greenwood, IN  26142 USA, FAX 1-317-888-2195,
          or send email to omb@asp-shareware.org.  In communication
          with the OMB please include a telephone number and/or FAX if
          available.
          PC-ECAP Reference Manual                          page 5

          System Requirements:


               *    IBM PC or compatible with at least a 286 processor.

               *    PC or MS-DOS 2.0 or later.

               *    One floppy disk drive.

               *    384K of system memory.

               *    A graphics card is recommended for best
                    performance.  But if all you have is a Monochrome
                    Display Adapter, PC-ECAP will even graph its
                    results on that - though the resolution will be
                    much lower.

               *    An IBM/Epson, HP LaserJet or HP DeskJet compatible
                    printer if hard copy is desired.  Most printers
                    used with IBM and IBM compatible computers support
                    one of these standards.



          Attention users of MS-DOS version 3.2


          Version 3.20 of MS-DOS contains a bug that can cause
          unexpected results in programs that use floating-point math
          (eg. PC-ECAP).

          You do not need to read any further unless your system has
          ALL of the following characteristics:

              1.    You use MS-DOS version 3.20.
              2.    You boot from a hard-disk drive.
              3.    Your system has a math coprocessor (for instance,
                    an 8087 chip).
              4.    You run programs that use floating-point math
                    (eg. PC-ECAP).

          For systems that satisfy all of the preceding conditions,
          you may be able to eliminate floating-point math problems by
          installing a small patch in DOS.  Please contact Microsoft
          for complete details on this.

          Since this bug has been fixed in later versions of MS-DOS,
          you may also want to consider upgrading your DOS to a more
          recent version.
          PC-ECAP Reference Manual                          page 6

          Before You Begin

          The very first thing that you should do before going any
          further is to make a backup copy of your distribution disk.
          To do this just use the DOS command DISKCOPY.  This will
          work whether or not you have two floppy disk drives.  It
          also doesn't matter if the diskette that you want to copy to
          is formatted or not.  DISKCOPY will format it for you.

          From the DOS prompt type this:

               DISKCOPY A: B:

          You will be asked to "Insert source diskette in drive A:"
          This should be your original PC-ECAP disk.  Continue to
          follow the directions on the screen and you will have your
          backup copy.


          Installing PC-ECAP

          We have included an "Install" program with PC-ECAP to make
          installation very easy.  The Install program will not do
          anything "funny".  It will not modify your AUTOEXEC.BAT or
          your CONFIG.SYS files.  What it will do is create a
          subdirectory on your hard drive called "\ECAP".  Then it
          will copy all the needed PC-ECAP files from your floppy
          drive to that subdirectory.  If you have any PC-ECAP program
          files (NOT data files) prior to version 2.0, they will be
          deleted.  That's all.  It is strictly for your convenience.
          The default "from" drive is the drive where INSTALL.EXE is
          located and the default "to" drive is drive C:.  These may
          be changed to any other drives or directories as needed.

          If you don't have a hard drive, you don't need to proceed
          any further.  Skip the rest of this section and use your
          backup copy as your working disk.

          To use the install program, insert your backup copy of
          PC-ECAP into your floppy drive and type:

                    A:INSTALL

          Follow the directions and before you know it, you will have
          PC-ECAP on your hard drive.
          PC-ECAP Reference Manual                          page 7

          Quick Start

          Although there is no substitute for reading this entire
          manual, I know there are those of you who can't wait to try
          a new program.  So for those who like to try-first-read-
          later, this will give you a taste of what PC-ECAP can do.

          Start PC-ECAP by typing:

               ECAP

          at the DOS prompt.

          From the main menu choose the "Select input file" selection.
          Select EXAMPLE1.DAT as your input file.  The circuit
          described by EXAMPLE1.DAT is a simple RC low-pass filter and
          is shown below.


                        1        1.59K                 2
                         ------/\/\/\/\------*---------
                                             |
                                             |
               input                      ___|___  .1uf      output
                                          _______
                                             |
                                             |
                                          0  |
                         --------------------*----------


          Now from the main menu choose "Analyze circuit".  The
          analysis will begin and you will see the results as the
          program progresses.  When the analysis is complete, the
          results will be plotted on your display.  First you will see
          a plot of Magnitude vs. Frequency.  If you press any key
          other than ESC you will get a plot of Phase vs. Frequency.
          Pressing any key (other than ESC) again will show you
          Magnitude again.  When you are finished, press ESC to return
          to the main menu.

          As I said, this is a taste - for the details read on.
          PC-ECAP Reference Manual                          page 8

          Printer Configuration

          PC-ECAP supports four printer types.  To properly print on
          your printer, you must configure the program for the printer
          that you are using.  The "Change program settings" choice of
          the main menu has an option to "Pick a printer to use".
          Select your printer from the list given.  One of these types
          should be a good match for your printer.  Refer to the
          "Change program settings" section in the manual for more
          details.  Be sure to save your choice.

          There might be times when you want to print on single sheets
          of paper instead of the more common continuous forms paper.
          If this is the case, you will need to use the DOS MODE
          command before running PC-ECAP.

          Each time that a single page has completed printing, the
          printer stops and returns an error.  Depending on the
          printer, this error may be "OFF-LINE" or "OUT-OF-PAPER".  In
          any case, what gets reported to the program is a "WRITE
          FAULT ERROR".  PC-ECAP was unable to write to the printer.

          The DOS MODE command provides a way around this problem.
          MODE will enable an "infinite retry on printer".  Which
          really means - return a printer busy signal and continue
          retrying until the printer accepts the output.  When this is
          done, a "WRITE FAULT ERROR" will not be reported to PC-ECAP
          and the program will simply wait for the next sheet of
          paper.

          If your DOS version is 4.01 or less, type this before
          running PC-ECAP:

               MODE LPT1:,,P

          If you are running DOS 5 or DOS 6, MODE has a slightly
          different format:

               MODE LPT1: RETRY=B

          If you are printing to a printer other than LPT1, you should
          change the MODE command accordingly.  See your DOS manual if
          you need more help on this.

          If you need to use the MODE command you should add it to
          your AUTOEXEC.BAT file.  This setup will install it
          automatically.
          PC-ECAP Reference Manual                          page 9

          Users of PC-ECAP versions prior to version 2.0

          Before version 2.0, all numbers were represented and stored
          in BCD format.  With version 2.0, numbers are now stored in
          IEEE binary format.  However, PC-ECAP can read any result
          files stored in BCD.  When you access an old file you will
          see the message "Converting file format . . .".  This
          conversion is done "on the fly", meaning the converted file
          is not saved.  To avoid this file conversion every time you
          view an old file, simply rerun an analysis.


          Accessing PC-ECAP Circuit Files in Other Directories

          If you are running DOS 3.0 or later you may easily work with
          circuit files in other directories or on other drives.  To
          do this you must have the directory that contains the
          PC-ECAP program files listed in your PATH.  You should have
          a line similar to this in your AUTOEXEC.BAT file:

               PATH=C:\ECAP

          Yours will not be EXACTLY like this one.  You may have
          additional directories listed or the drive letter may be
          different.  The important thing is that the PC-ECAP drive
          and directory be part of the PATH.  You may want to refer to
          your DOS manual if you need more information on this.

          Once your PATH is set up, DOS will know where to find
          PC-ECAP no matter where you are.  And under DOS 3.0 or
          later, PC-ECAP will know where to find any additional files
          it needs to run.


          Memory Requirements

          As of PC-ECAP version 2.1, you can analyze circuits with up
          90 nodes.  Older versions of the program had a limit of 40
          nodes.  Analysis of a 90 node circuit requires that you have
          450K bytes of free memory.  That is, memory left after you
          load any memory resident programs.  If you don't have this
          much memory available, don't worry.  You will just be
          limited to circuits having fewer nodes.  If you have less
          than 450K free, PC-ECAP will give you its estimate of the
          largest circuit that you may analyze on program start up.
          Keep in mind that this is an estimate and therefore it is
          not exact.  Therefore, if you are told that you have enough
          memory to analyze circuits with up 57 nodes, and you have a
          circuit with 58, give it a try.  It may very well work.

          Also please note, that since node numbers start at 0, the
          highest possible node number is 89.
          PC-ECAP Reference Manual                          page 10

          PC-ECAP can also use upper memory blocks (UMB's) for its
          memory needs.  You must be running DOS 5 or greater and have
          a line similar to the following in your CONFIG.SYS file:

               DOS=UMB

          You can check on UMB availability with the DOS MEM command.
          Typing "MEM /C" will list the conventional and upper memory
          in your system.  If no upper memory is listed, either your
          hardware doesn't support UMB's or your system is not set up
          properly.  See your DOS manual if you need help with this.
          PC-ECAP will try to use any free upper memory listed.

          The estimate given at program startup will not take into
          account any UMB's.  These blocks can be highly fragmented,
          so it is not possible to know if they are large enough to
          use until they are needed.


          Network / Multi-User Operation

          PC-ECAP has built-in support to run on a local area network.
          Your network must support DOS file-sharing (added with DOS
          version 3.0).  When running on a network, multiple users may
          share circuit description and analysis result files.

          PC-ECAP imposes two main restrictions when accessing files
          on a network.  If a file is being edited, no one else may
          run an analysis on it.  If a circuit is being analyzed, no
          one may view or output the results until the analysis is
          complete.  In general, individual file access at any one
          time is restricted to operations that make sense.  For
          example, a circuit whose analysis is only partially complete
          can't be viewed.  Of course you may do any operation you
          choose if you are the only person using a particular file.

          If you attempt to access a file that is already in use,
          PC-ECAP will display the message, "File is currently being
          used by someone else".  You may wait until that file is
          available or you may choose to work on a different file.

          You should also be aware that PC-ECAP maintains a single
          configuration file.  So if you change some of the program
          settings, and then write these changes to disk, the next
          person on the network to run the program will get these new
          settings.
          PC-ECAP Reference Manual                          page 11

          Getting Started

          PC-ECAP is started by typing the following command at the
          DOS prompt:

                    ECAP   [ options ]

          The optional command line switches are used to manually set
          the video mode.  Since PC-ECAP is usually able to do this
          automatically, these options should not be needed by 99% of
          computers.  They are covered separately in Appendix A.  If
          you have trouble seeing the main menu after the opening
          screen, please refer to this appendix.

          When PC-ECAP is started, you will first see the main menu.
          The program has been designed to be very easy to use, and
          the menu system plays an important part in reaching this
          goal.  All menu choices may be selected in either one of two
          ways.  First, a selection may be made by typing the first
          letter of an item.  These are highlighted so they stand out.
          Selection may also be made by using the cursor keys (up
          arrow, down arrow, home and end) to highlight a choice.
          When "ENTER" is pressed the selection is made.  The program
          will do its best to logically anticipate your next choice.
          For example, after editing a circuit description and
          returning to the main menu, the choice "Analyze circuit"
          will be highlighted - assuming that after editing, you most
          likely will want to analyze your circuit.

          MAIN MENU Descriptions

          Select input file

               This selection will display an alphabetically sorted
               list of all the circuit description files in your
               current directory.  Use the cursor keys to select a
               file to use.  If you see "more . . ." displayed at the
               beginning or end of the list, this means that there are
               additional files on another page.  You can use the PgUp
               or PgDn keys in addition to the up arrow, down arrow,
               left arrow, right arrow, home and end keys to view
               them.  Once your choice is highlighted just press ENTER
               to select it.

               PC-ECAP also has a "Speed Search" feature.  To use it,
               type the first letter of the file that you want to
               select, followed by enough letters to uniquely specify
               it.  In most cases all it takes is 2 or 3 letters.
               Your desired file will be highlighted.  Press ENTER to
               select it.
          PC-ECAP Reference Manual                          page 12

               If you want to select a file that is not listed (for
               example - a new circuit description that you want to
               input) press F2.  A window will appear asking for the
               filename.  Type the filename and press ENTER.  All
               filenames should be eight characters or less in length.
               If you type in more than eight, only the first eight
               will be accepted.  A file extension is optional, if it
               is omitted the extension ".DAT" will be appended to the
               filename.  If a filename has an extension other than
               ".DAT", the ".DAT" extension will be substituted in its
               place.

               You can delete a highlighted file by pressing F3.  When
               you do so, a window will appear asking, "Delete File?".
               Answer "Yes" to delete.  "No" or ESC will abort the
               operation.

          If at any time you want to abort the current operation,
          pressing the ESC key will return you one level up in the
          program.

          Edit input file

               This starts the built-in full screen editor.  The file
               that you want to edit must be selected first.  If no
               file is selected, you will be sent to the "Select input
               file" screen and then returned to the editor.

               The editor is very straight forward to use, just type
               each line followed by the ENTER key.  When in the
               editor these keys have special meaning:

               Right Arrow  - move one character to the right.

               Left Arrow   - move one character to the left.

               Home         - move to the beginning of the line.

               End          - move to the end of the line.

               Up Arrow     - move one line up.

               Down Arrow   - move one line down.

               Ctrl Home    - move to the beginning of the file.

               Ctrl End     - move to the end of the file.

               PgDn         - move 20 lines down.

               PgUp         - move 20 lines up.

               Del          - will delete the character directly above
                              the cursor.
          PC-ECAP Reference Manual                          page 13

               Backspace    - will delete the character to the left of
                              the cursor.

               Tab          - move cursor 4 spaces to the right.

               Shift-Tab    - move cursor 4 spaces to the left.

               Ins          - will toggle between the insert and
                              replace modes.  In the insert mode the
                              cursor will change to a block cursor and
                              any characters typed will be inserted
                              between any characters already on the
                              screen.  When in replace mode, any
                              characters typed will type over those on
                              the screen.

               In addition to these special keys, five function keys
               have special meaning.  Press them alone or in
               combination with the "Alt" key to access the following
               features.

               F1 Help

                    One of the features that has been added to make
                    PC-ECAP easy to use is the on-line help.  When F1
                    is pressed a window will appear containing useful
                    information on items such as circuit element
                    description formats, analysis range and sweep
                    type, value types and examples.  You can move
                    through these with the PgUp and PgDn keys.  When
                    you are ready to continue editing, pressing F1
                    again or the ESC key will close the window and let
                    you edit.

               F2 Model Maker

                    The model maker allows you to more accurately
                    model bipolar transistors.  The transistor model
                    used is the Hybrid-Pi model.  Despite its
                    simplicity, this model gives quite good results
                    for analysis up to about one half of the
                    transistor's cutoff frequency (Ft).

                    When the model maker is activated, a window will
                    appear.  You will first be asked for the node
                    numbers of the transistor.  Enter these pressing
                    the ENTER key after each entry for base, emitter,
                    and collector.  You next have to answer four
                    questions.  You will be asked (and need to know)
                    the following:
                    
                    Transistor DC collector current - hopefully you
                    will know this.  If not, try your best guess.
          PC-ECAP Reference Manual                          page 14

                    Transistor current gain or Beta - since the gain
                    of bipolar transistors varies with collector
                    current, the number that you enter here should be
                    at the collector current specified above for best
                    results.  Usually it is available in the data
                    sheet for the transistor.

                    Transistor Gain-Bandwidth product (Ft) - this also
                    should be at the collector current entered above
                    (check the data sheet).

                    Transistor common base output capacitance - this
                    is just the base to collector capacitance.
                    Usually it is listed as Cobo in the transistor
                    data.  (Which means output capacitance common base
                    with the emitter open).

                    After all the information is entered, the window
                    will close and components for the model will be
                    inserted into your circuit description after the
                    current cursor line.

               F3 Insert Line

                    Pressing F3 will insert a blank line above the
                    current cursor line and move the cursor line and
                    all lines below it down.

               F4 Delete Line

                    Pressing F4 will delete the current cursor line
                    and move all lines below it up.  The deleted line
                    will be placed in the cut buffer and can be pasted
                    if desired.

               F5 Find Component

                    The Find Component feature is useful to find
                    circuit elements in your circuit description file.
                    Just press F5, enter the element to be found, and
                    the line containing the element will be
                    highlighted with the cursor positioned there.  If
                    the element does not exist, a "Component not
                    found" message will appear.

               Alt-F1 Net List

                    This feature can make it easier to track down
                    errors in your circuit description.  The Net List
                    is a node by node list of all the circuit elements
                    that make up your description.  By comparing the
                    connections in this list to your circuit's
                    schematic, you can verify that your circuit is
                    described properly.
          PC-ECAP Reference Manual                          page 15

                    When the Net List is selected, you will be asked
                    whether you want your list sent to the screen or
                    to a defined printer.  If you select screen, a
                    window will appear listing your circuit's nodes
                    and their attached components.  Use the cursor
                    keys to move through this list.  To close this
                    window and return to editing, just press ESC.

               Alt-F2 Rename File

                    You may change the name of a circuit description
                    file by selecting "Rename File".  A window will
                    appear asking for your new file name.  Type the
                    new name and press ENTER.  ESC will close the
                    window and leave the existing file name unchanged.
                    When you rename and save a file, the old named
                    file will still exist.  This is useful if you have
                    a circuit that is very similar to an existing
                    circuit description.  You can modify the existing
                    description and save it under a new name. If you
                    want to delete the old named file, you can do so
                    from the "Select input file" menu.

               Alt-F3 Paste Line

                    This option will insert a line saved in the cut
                    buffer above the current cursor line and move the
                    cursor line and all lines below it down.

               Alt-F4 Copy Line

                    Will copy the current line into the cut buffer.
                    Used with the Paste Line feature above.

               Alt-F5 Find Next

                    This will find the next component meeting your
                    search criteria as specified under "Find
                    Component".  If you have asked for a unique
                    component, you won't be able to find a "next".
                    This option is most useful when you want to find
                    all occurrences of a part, such as all capacitors
                    or all resistors, etc.

               Leaving The Editor

               When you are finished with your editing, press the ESC
               key.  If you have made any changes to the file, a
               window will pop up and ask, "Save Changes?".
               Answer "Y" to save all changes, or "N" to ignore all
               changes.  An ESC will cancel the exit, if you have
               changed your mind.
          PC-ECAP Reference Manual                          page 16

          Analyze circuit

               This choice will begin the actual analysis of the
               circuit selected.  If a file containing the circuit
               description has not been selected, you will first be
               sent to the "Select input file" screen and then
               returned to begin analysis.

               PC-ECAP will subject your circuit to a 1 volt signal at
               the selected input node and then calculate the desired
               response at the selected output node.  The input signal
               is from an ideal voltage source and therefore it can
               drive any impedance.  Any output node selected will not
               be loaded by PC-ECAP.

               This analysis is repeated for each of the frequency
               points within the specified input range.  The number of
               points is determined by the "Change the number of
               sample points" option under the "Change program
               settings" choice of the main menu.  Its use will be
               fully explained under that heading.  If you are doing
               an AC analysis, PC-ECAP will display magnitude and
               phase results as the analysis progresses.  For a
               transient analysis the individual points are not
               available until the analysis is complete.  The results
               of the analysis are also saved in a disk file.  The
               file will have the same name as the circuit description
               file but will have a file extension of ".OUT".
          PC-ECAP Reference Manual                          page 17

          Plotting results

          When the analysis is finished, the results will be plotted
          on your display.  For all display adapters other than VGA,
          PC-ECAP will use the highest resolution that your display
          adapter supports.  VGA adapters will be run in EGA mode (640
          x 350).  The resolution used will be as follows:

                         CGA          640 x 200

                         EGA          640 x 350    enhanced display

                                      640 x 350    monochrome display

                                      640 x 200    color display

                         Hercules     720 x 348

                         VGA          640 x 350    monochrome or color

                         MCGA         640 x 480    monochrome or color

                         AT&T         640 x 400   

                         MDA          80 x 25

          When viewing the graphs on most display adapters you have
          the options "Zoom", "Print", "Full" and ESC.  The MDA only
          has "Print" and ESC.

          "Zoom" allows you to enlarge an area of a graph.  Press the
          'Z' to display two vertical bars with an attached bottom.
          You may continue to press 'Z' to narrow the bars.  The
          number of times this is possible depends on the number of
          sample point you have selected for this analysis.  When the
          bars are at their narrowest, they encompass 35 sample
          points.  When you have the bars at the desired width, you
          can position them horizontally by pressing the Right arrow,
          Left arrow, Home or End keys.  When the bars are where you
          want them, press ENTER to zoom up on the area selected.

          When zooming, you may also use the Up arrow and Down arrow
          keys to position the bottom dashed line.  Moving this bar
          sets a minimum vertical scale for your graph.  This can be
          very useful to help view small variations in amplitude.

          You may press 'F' at any time for a "Full" screen display of
          your graph.  This simply presents the graph as it was
          originally displayed.

          You may also press 'P' at any time to get a hard copy print
          out of just your graphs.  The printout will be Zoomed if the
          graph is Zoomed on your display.  All graphs for your
          analysis will be printed.

          Pressing ESC will return you to the main menu.  Any other
          key will cycle through the various plots.
          PC-ECAP Reference Manual                          page 18

          View output data

               This selection allows you to view the results of
               circuits that have been previously analyzed.  The
               results will be listed in tabular form on the display.
               You can use the cursor keys to move through them.  The
               cursor keys that are active under this selection are
               the following:

                    Up Arrow     - scroll up one line.

                    Down Arrow   - scroll down one line.

                    PgUp         - scroll up 19 lines.

                    PgDn         - scroll down 19 lines.

                    Home         - display the first 19 lines.

                    End          - display the last 19 lines.

               The analysis results can also be plotted on the display
               by pressing the F1 function key.  Plotting works the
               same way as described in the "Analyze circuit" section.
               Pressing any key except 'Z', 'F', 'P' or ESC will cycle
               through the various plots.  Pressing ESC will return
               you to the tabular listing of the data. Press ESC again
               to return to the main menu.

          Output to printer

               PC-ECAP will normally send the results of an
               analysis to a printer selected under the "Change
               program settings" option.  If desired, the results can
               instead be sent to a disk file for printing later.  The
               file will have a filename that is the same as the file
               selected, but with a file extension of ".PRN".

               Partial output listing

               This choice will output a listing of the circuit
               description at the time of analysis and high resolution
               plots of the results.

               Full output listing

               Choosing this option will output a listing of
               the circuit description at the time of analysis, a
               tabular listing of the analysis results, and high
               resolution plots of these results.

               For printed output it is necessary to have a printer
               that is compatible with IBM/Epson, HP LaserJet or HP
               DeskJet printers.  Most printers used with IBM
               compatible computers support one of these standards,
          PC-ECAP Reference Manual                          page 19

               although in a few cases it may be necessary to select
               the proper mode by means of a switch on the printer.
               Be sure you have configured PC-ECAP for your particular
               printer type.  This is done under the "Change program
               settings" option of the main menu.  (see next section
               for details).

          Change program settings

               PC-ECAP allows you to configure certain aspects of its
               operation.  The configuration information is saved in a
               disk file that is read every time the program is run.
               The name of this file is "PC-ECAP.CFG".  If this file
               is not present it will be created.  This should only be
               necessary the very first time you run PC-ECAP.  The
               file will have as defaults: 70 sample points for
               analysis, LPT1 selected as the output destination, and
               an IBM/Epson 9 pin printer selected as your printer
               type.  Any of these may be changed by means of this
               menu.

               Change number of sample points

               When an analysis is performed, the desired range is
               divided into a number of sample points.  The number of
               points may be set to 35, 70, 140, 280 or 560.  It
               should be noted that you must obviously make a choice
               between the high analysis resolution provided by
               selecting 560 sample points and the faster
               computational speed offered by selecting 35 points.
               The number of points you select really depends on the
               circuits that you analyze.  I have found that for most
               circuits 70 sample points works quite well.  You should
               increase the number of points if you have a circuit
               that has abrupt changes in its response.  You may also
               need to increase the number of points if you analyze
               circuits over a very wide frequency or time range.

               Select output destination

               The output from PC-ECAP can be sent to a printer
               designated as LPT1, LPT2, or LPT3.  Alternately output
               may be sent to a disk file for later printing.  For
               printed output, select the port that you have your
               printer attached to (normally this will be LPT1).

               Pick a printer to use

               PC-ECAP supports four different printer types.  One of
               these types should be a good match for just about any
               printer.  The supported printer types are: IBM/Epson 9
               pin, HP LaserJet (or HP DeskJet), Epson 24 pin and IBM
               24 pin.  Just choose the type that matches your
               printer.  Since some printers can emulate more than one
               type, be sure that your printer and PC-ECAP are both
          PC-ECAP Reference Manual                          page 20

               configured for the same printer type.  After you make
               your selection, it is important that you "Write changes
               to disk" (see next choice).  If you don't save your
               printer configuration, PC-ECAP will not be setup
               properly the next time you use it.  This only needs to
               be done once.

               If you have an HP DeskJet printer, you should select HP
               LaserJet as your printer type.

               HP LaserJet or HP DeskJet users have an additional
               choice after the printer type is selected.  You will be
               asked "2 graphs on page?".  In almost all cases you
               should answer "Yes" to this question.  If you have an
               HP DeskJet, you MUST answer "Yes".  If you answer "No"
               and have an HP LaserJet, graphs will print in landscape
               mode (sideways).  This option was added mainly to
               support older HP LaserJet series I printers.  These
               printers don't have enough memory to print two graphs
               on a single sheet of paper.  The option to print in
               landscape mode may be occasionally useful to users of
               newer HP LaserJet printers.  But since graphic
               resolution is the same for either choice, most people
               will favor using less paper over full page graphs.

               Some printers allow you to manually set a particular
               font, pitch or mode.  DO NOT DO THIS.  On most printers
               this will override any printer commands that your
               computer may send, and PC-ECAP's printed output will
               not print properly.  If you have a problem with printed
               output, insure that your printer is in "Pgm" mode.
               When in "program" mode, your printer will follow your
               program's commands, and your printed output will appear
               as intended.

               Write changes to disk

               This selection will write any changes in configuration
               to the "PC-ECAP.CFG" file.  Select this option to make
               the changes you have made carry over to the next
               session of PC-ECAP.  If the changes are not written to
               disk, they will be in effect only for your current
               session.

               Return to main menu

               Returns you to the main menu.

          Quit this program

               Ends your current session with PC-ECAP and returns you
               to DOS.
          PC-ECAP Reference Manual                          page 21

          Analyzing a Circuit Using PC-ECAP

          The first step in analyzing any circuit is to draw the
          circuit on a piece of paper.  Next number all the nodes in
          the circuit.  A node is any connection of 2 or more
          components.  Node numbers must be non-negative integers.
          There are two rules that you must follow when numbering
          nodes, first ground or the common connection between input
          and output must always be designated as node number 0.
          Secondly, although the nodes may be numbered in any order,
          none may be skipped.

          PC-ECAP has a limit of 90 nodes and can handle up to 1000
          components.  Some components count as more than one circuit
          element.  You can use the following as a guide;


               Resistors, Capacitors, Inductors, Transmission
               lines, Fet's and Transconductance amplifiers
               each count as one circuit element.

               OpAmps and Bipolar transistors count as two.

               Transformers count as four.


          So it is possible to have fewer than 1000 components in your
          circuit and still exceed this limit.  Although, in practice,
          it is highly unlikely that you will reach this limit.
          PC-ECAP Reference Manual                          page 22

          Input Format

          The input format of a PC-ECAP circuit description is easy to
          learn and remember.  Fields describing a component are of
          the free format type and are simply separated by spaces.
          Circuit element names should begin with a letter designating
          the type of circuit element and may optionally be followed
          by up to 14 additional alphanumeric characters.

          Values used to describe a circuit element may be integer
          (100), floating point (1000.45), either an integer or
          floating point number followed by an integer exponent
          (1E-3, 4.7E6) or either an integer or floating point number
          followed by one of the following scale factors:

               P=1E-12   N=1E-9    U=1E-6    M=1E-3    K=1E3

                         MEG=1E6        G=1E9

          Letters immediately following a number that are not scale
          factors are ignored, and letters immediately following a
          scale factor are ignored.  So 10, 10ohms and 10Hz all
          represent the same number, and u, uf and umhos all represent
          the same scale factor.  Note that 1000, 1000.0, 1000Hz, 1E3,
          1.0E3, 1K and 1KHz all represent the same number.

          In addition, some values may also be expressed in "European"
          format.  This format has one or more digits followed by a
          scale factor that also takes the place of a decimal point,
          followed by one or more digits.  For example, 1500 would be
          expressed as 1K5.  When values are in this format, these
          scale factors are recognized: R, K, M.  `R' is equal to a
          factor of 1.  `K' is equal to 1000, as above.  `M' is equal
          to a factor of 1E6.  Please note the difference between this
          use of `M' and `M' in the non-European format above.  When
          `M' is placed at the end of a number it multiplies the
          number by 1E-3.  But when `M' is placed between two numbers,
          the multiplication factor is 1E6.  Be careful!


               Some examples:

               6R8 is 6.8,    5K1 is 5100,    4M7 is 4.7 million
          PC-ECAP Reference Manual                          page 23

          Circuit Element Description

          Resistors

               Rxxxx N1 N2 Value

          N1 and N2 are the two element nodes.  Value is the
          resistance in ohms.

          Examples:

               R1 1 2 100

               RLOAD 12 15 1K

          Capacitors

               Cxxxx N1 N2 Value

          N1 and N2 are the two element nodes.  Value is the
          capacitance in farads.

          Examples:

               C4 8 9 1uf

               COSC 2 3 22pf

          Inductors

               Lxxxx N1 N2 Value

          N1 and N2 are the two element nodes.  Value is the inductor
          value in henries.

          Examples:

               L3 7 0 10mh

               LTANK 4 5 56uh

          Transformers

               Txxxx +Pri -Pri +Sec -Sec  N

          +Pri and -Pri are the nodes for the transformer primary.
          +Sec and -Sec are the nodes for the transformer secondary.
          N is the turns ratio between primary and secondary (Np/Ns).
          The + and - signs denote the phasing of the windings,
          e.g. the +Pri node will be in phase with the +Sec node.

          Example:

               T1 3 0 4 5 10turns
          PC-ECAP Reference Manual                          page 24

          Transmission Lines  (lossless)

               Xxxxx N1 N2 Impedance Length

          N1 and N2 are the two ends of the transmission line.  The
          line model used is unbalanced, so N1 and N2 are referenced
          to ground.  The line impedance is in ohms.  The Length is
          specified in meters.

          Example:

               X1 1 2 50 3

          Bipolar Transistors (both NPN and PNP)

               Bxxxx NB NE NC Beta Rbe

          NB, NE, and NC are the base, emitter and collector nodes
          respectively.  Beta is the Transistor current gain.  Rbe is
          the equivalent base-emitter resistance (in ohms) used in the
          Hybrid-Pi transistor model.

          Example:

               B1 9 0 11 100 1250

          Field Effect Transistors  (both JFETs and MOSFETs)

               Fxxxx NG NS ND Gm

          NG, NS, and ND are the gate, source, and drain nodes
          respectively.  Gm is the FET transconductance in mhos
          (Amps/Volt).

          Example:

               F2 3 4 0 2000umhos

          Operational Amplifiers

               Oxxxx N+ N- NO Gain Rout

          N+, N-, and NO are the non-inverting input, inverting input
          and output nodes respectively.  The opamp output is
          referenced to ground (node 0).  Gain is the open loop gain
          of the opamp, usually somewhere between 10,000 and 1 million
          times.  Rout is the open loop output resistance for the
          opamp.  Real opamps usually have an output resistance
          between 10 and 150 ohms.

          Example:

               O1 1 2 2 100k 75
          PC-ECAP Reference Manual                          page 25

          Transconductance Amplifiers

               Gxxxx N+ N- NO+ NO- Gm

          N+ and N- are the non-inverting input and inverting input.
          NO+ and NO- are the non-inverting output and the inverting
          output.  Please note that these outputs are floating.  In
          other words the actual output is not from either output to
          ground, but is developed between the outputs.  Either output
          (but not both) may be tied to ground if a single ended
          output is desired.  Gm is the amplifier transconductance in
          mhos (Amps/Volt).  The transconductance amplifier may be
          used in its own right or it may be used to perform a voltage
          to current conversion, sometimes useful when simulating
          other devices.

          Example:

               Gxxxx 1 2 3 0 100mmhos


          A Few Words About Transconductance Amplifiers

          Although most people are familiar with bipolar transistors
          and operational amplifiers, not as many know about
          transconductance amplifiers.  These amplifiers are another
          variation of a dependent source.  The common bipolar
          transistor is a current controlled current source; A small
          current entering the base controls a much larger current
          flowing between the collector and emitter.  The opamp is a
          voltage controlled voltage source; A very small input
          voltage effectively controls a much larger voltage swing at
          the output.  With this said, a transconductance amplifier
          can be described as a voltage controlled current source; A
          small voltage difference between the two inputs controls a
          current flowing either into or out of the output.  In our
          case this current will flow from one output to the other.


          Valid Circuit Elements

          All of the lines that make up a PC-ECAP circuit description
          file must either begin with one of the previously mentioned
          elements, be blank, or be a comment.  To add a comment to
          your circuit description, begin the line with a semicolon.
          An example comment might be:

               ; this begins the second filter section

          If a line begins with something other than a circuit
          element, a blank line, or a comment, PC-ECAP will abort the
          analysis and flag the bad line.
          PC-ECAP Reference Manual                          page 26

          Specifying AC Analysis Parameters


          Once your circuit has been described you need to determine
          how it will be analyzed.  PC-ECAP will subject your circuit
          to a 1 volt signal at the selected input node and then
          calculate the response at the selected output node.  In an
          AC analysis, the frequency of the input signal can be swept
          over the specified range in either a linear or logarithmic
          fashion.

          The PLOT statement is used to tell PC-ECAP which node of
          your circuit will be used for the input, which node will be
          used for the output, the frequency range that you want to
          analyze, the sweep mode (linear or logarithmic) and the
          analysis type.  PLOT should be the last statement in your
          description.

          This is the AC format for the PLOT statement:


            PLOT NI NO Start-freq. Stop-freq. Plot-mode Plot-type


          PLOT may optionally be abbreviated to P.  NI is the
          circuit's input node.  NO is the circuit's output node.
          Start-frequency is simply the beginning frequency for the
          analysis.  Stop-frequency is the upper frequency limit of
          the analysis.  Plot-mode specifies whether a linear or a
          logarithmic frequency sweep is to be performed.  This may be
          abbreviated to 3 letters (LIN or LOG) if desired.

          Plot-type may optionally be used to specify the analysis
          type.  If it is not specified, magnitude and phase will be
          calculated.  To calculate group delay, impedance, VSWR or
          return loss, you must provide this parameter.


               for:                   Plot-type is:

          group delay                   Delay

          impedance in magnitude        ZPolar
           and phase format

          impedance in Real and         ZRectangular
           Imaginary format

            VSWR                        SWR    <reference impedance>
          (voltage standing
               wave ratio)

          return loss                   RLoss  <reference impedance>


          Plot-type may be abbreviated to the letters that are
          capitalized.
          PC-ECAP Reference Manual                          page 27

          Impedance, VSWR (voltage standing wave ratio) and return
          loss calculations will be done at the input node specified.
          This doesn't mean that you can't calculate an output
          impedance instead.  If your circuit's output is node 8, and
          you are interested in its output impedance, just specify
          node 8 as the input node for the PLOT statement.  You can
          look at it this way, to determine impedance, PC-ECAP must
          apply an excitation signal to your circuit.  This signal is
          always applied to the node listed as the input node for your
          circuit.

          For VSWR and return loss, a reference impedance must also be
          specified.  This is the impedance that your circuit is
          supposed to be matched to.  This is usually 50 or 75 ohms,
          but it may be any positive value.

          As an example of what we have been discussing, we might have
          a circuit where node 2 is the input and node 5 is the
          output.  The lowest frequency that we want to look at is 100
          Hz and the highest frequency is 10 KHz.  We are only
          interested in magnitude and phase vs frequency.  And we want
          to sweep this range logarithmically.

          This PLOT statement will specify all this:

               PLOT 2 5 100HZ 10KHZ LOG

          For another example, we have a circuit with node 1 as its
          input.  We are interested in determining the input VSWR vs
          frequency.  The input is supposed to match 50 ohms, and
          operate from 7.0 MHz to 7.3 MHz.

          This is the PLOT statement that will do the job:

               PLOT 1 5 7MEG 7.3MEG LIN SWR 50

          Please note that for impedance, VSWR or return loss
          calculations, the output node specified in the PLOT
          statement is unimportant.  It is ignored.


          What is Group Delay anyway?

          If a circuit is designed to pass all important frequencies
          with equal amplitude and have absolutely linear amplitude
          characteristics, a waveform may still pass through badly
          distorted.  The problem is delay distortion; if all
          frequency components do not pass through a circuit with the
          same time delay, the output waveform will not look the same
          as the input.  Group delay is the rate of phase shift vs
          change of frequency, and is defined as:

                                   1    d0
                    group delay = --- x ---  seconds
                                  360   df
          PC-ECAP Reference Manual                          page 28

          Specifying Transient Analysis Parameters

          PC-ECAP also has the capability to analyze the transient
          behavior of a circuit.  This feature can give you important
          information about a circuit's response vs time.  You have a
          choice of eight different input waveforms for analysis.  In
          addition, a circuit's impulse response can also be
          calculated.

          As with an AC analysis, the program will subject your
          circuit to a 1 volt (peak) signal from an ideal voltage
          source.  The input waveform can be one of the following: a
          step (unit step, and two modified step functions), pulse,
          ramp, square wave, triangle wave, or sine wave.  You may
          optionally add noise to any of these waveforms.

          The PLOT statement is used to specify all the parameters
          needed for a transient analysis.  This is its format:


            PLOT NI NO TStart TStop TRAN Wave-Type TPeriod NOISE


          PLOT may be abbreviated to P.  NI is the circuit's input
          node.  NO is the circuit's output node.

          TStart is a time offset for the input waveform.  The input
          waveform will be delayed by the amount specified by TStart.
          It can be helpful to delay the rising edge of the input when
          analyzing some circuits.

          TStop is just the final time for the analysis.  TRAN tells
          PC-ECAP that a transient analysis is desired.

          Wave-Type selects the waveform at the input and should be
          one of the these:


               STEP

               This is a unit step.  The wave is 0 volts when time
               is less then TStart.  At TStart, the voltage goes to 1
               volt and stays there.


               STEP1  [rise-time]

               This is a modified step function.  It behaves like the
               STEP just discussed, but has a rise time that is shaped
               by a COSINE function.  A rise time must be specified
               for this function.  The rise time is the amount of time
               the leading edge takes to go from 20% to 80% of its
               final value.  If a rise-time is not specified or is
               zero, it will default to TStop / 8.
          PC-ECAP Reference Manual                          page 29

               STEP2  [rise-time]

               This is a another modified step function.  It behaves
               like the STEP discussed before, but has a rise time
               that is shaped by a RAMP function.  A rise time must be
               specified for this function.  The rise time is the
               amount of time the leading edge takes to go from 20% to
               80% of its final value.  If a rise-time is not
               specified or is zero, it will default to TStop / 8.


               PULSE  [pulse-width]

               This pulse is 0 volts at any time less than TStart.  At
               TStart, it goes to 1 volt and stays there for a time
               equal to "pulse-width".  After this time (TStart +
               pulse-width) the voltage returns to 0 for the remainder
               of the analysis.  "Pulse-width" must be specified.  If
               it is not or is zero, it will default to one-half
               "TStop".


               RAMP  [pulse-width]

               This waveform is 0 volts for any time less than TStart.
               At TStart the voltage will linearly increase, finally
               reaching 1 volt when time is equal to TStart + pulse-
               width.  At the next time step, the voltage will
               immediately return to 0.  As with the PULSE, "Pulse-
               width" determines the width of the RAMP and must be
               specified.  If it is not or is zero, it will default to
               one-half "TStop".


               SQRW  [frequency]

               This will generate a square wave.  At TStart the
               voltage will jump to +1 volts.  Half way through the
               cycle, the voltage will change to -1 volts.  This cycle
               will continue forever.  The frequency is determined by
               the "Frequency" parameter which must be specified.  If
               "Frequency" is missing, it will default to 1/TStop.


               TRIW  [frequency]

               This will generate a triangle wave.  At TStart the
               voltage will linearly increase to +1 volts.  A quarter
               way through the cycle, the voltage will begin to ramp
               down.  When the voltage reaches -1 volts, the ramp will
               reverse and start back up to +1 volts.  This cycle will
               continue forever.  The frequency is determined by the
               "Frequency" parameter which must be specified.  If
               "Frequency" is missing, it will default to 1/TStop.
          PC-ECAP Reference Manual                          page 30

               SINW  [frequency]

               This will generate a sine wave.  At TStart the voltage
               will increase to +1 volts.  A quarter way through the
               cycle, the voltage will reverse direction.  When the
               voltage reaches -1 volts, the wave will reverse and
               start back up to +1 volts.  This cycle will continue
               forever.  The frequency is determined by the
               "Frequency" parameter which must be specified.  If
               "Frequency" is missing, it will default to 1/TStop.


               IMPULSE

               This option will compute the impulse response for your
               circuit.  The impulse function is defined as a pulse of
               infinitely high amplitude with an infinitely short
               duration.  The area under this pulse (voltage x time)
               is equal to 1.  Although this pulse can't truly exist
               in the real world, it is nevertheless useful in some
               situations.  The impulse response always starts at time
               0.  TStart is ignored (but a value MUST still be
               supplied).


               NOISE

               Noise is an optional parameter that can be added to any
               of the waveforms described other then IMPULSE.  When
               present, pseudorandom noise is added to the wave
               specified.


          Computational Techniques Used in PC-ECAP Transient Analysis

          The method PC-ECAP uses to compute transient response is a
          bit unconventional and deserves some explanation.  It's not
          necessary to understand all of this in detail, but a basic
          understanding of the principals involved will help you get
          the most out of the program.

          You may have heard of something called a Fourier transform.
          This is a mathematical operation that can convert from the
          time domain (amplitude vs. time) to the frequency domain
          (amplitude vs. frequency).  With the Fourier transform you
          can take a waveform and break it down into the series of
          individual frequency components that make it up.

          As with most mathematical operations, there exists an
          inverse to the Fourier transform.  The Inverse Fourier
          transform can take a set of frequency components and
          construct a waveform in the time domain.  This is a very
          powerful tool.  It allows you to work in the frequency
          domain when convenient and then convert to the time domain
          only when desired.
          PC-ECAP Reference Manual                          page 31

          PC-ECAP can easily calculate the frequency response of a
          circuit (amplitude vs. frequency).  By using an Inverse
          Fourier transform, we can calculate what is called the
          Impulse response of the circuit.  If you know the Impulse
          response of a circuit, it is possible to find the response
          to ANY other waveform by a mathematical operation called
          convolution.  This is very powerful technique and certainly
          involves a lot of underlying mathematics.

          So, to calculate the transient response of a circuit,
          PC-ECAP first computes the magnitude and phase at a series
          of harmonically related frequencies.  Next it performs a
          Discrete Inverse Fast Fourier Transform.  At this point we
          have the Impulse response.  In the next step, a Discrete
          Convolution is performed between the Impulse response and
          the desired waveform that was specified at the circuit's
          input.  The result is the transient response of the circuit
          to the waveform specified.

          It is important to realize that the accuracy of the analysis
          depends on the number of sample points chosen.  The number
          of sample points determine not only the number of points
          that you wind up with in the time domain, but they also
          determine the number of frequencies used in the Inverse FFT.
          Choosing too few sample points will impair the accuracy of
          the analysis.

          How few is "too few"?  That depends on your circuit.  Every
          circuit that contains at least one capacitor or inductor has
          what is called a "natural frequency".  Also sometimes called
          the "natural response".  Some circuits have many "natural
          frequencies".  These are nothing more than the various time
          constants (for RC's or RL's) or resonant frequencies (for
          LC's) in a circuit.  If you have some background in
          electronic theory, these are the poles and zero's of a
          circuit.

          If you pick too few sample points, the program will not use
          enough frequencies to properly characterize your circuit.

          The time scale you select also effects the accuracy of your
          results.  If the time scale is large compared to the natural
          frequencies of your circuit, you will have to increase the
          number of sample points used.  If the time scale is too
          small, the analysis frequencies will start above the
          circuit's natural frequency and accuracy will suffer.

          For the problem of picking a time scale that is too short,
          the thing to remember is the Impulse response of a circuit
          must die out to zero in the time frame specified.  This is
          important and easily determined.  If you want to check this
          condition, specify IMPULSE as your Wave-Type.  You should
          see your circuit's response go to zero sometime before the
          TStop time.  If it doesn't, you must increase TStop.
          PC-ECAP Reference Manual                          page 32

          A circuit that has a large span of natural frequencies will
          require the most care to analyze.  For the low natural
          frequencies, the TStop time must be set large enough so the
          Impulse response dies out to zero.  At the same time, the
          number of sample points must be great enough to properly
          characterize the high natural frequencies.

          All this will make more sense when you actually analyze a
          few circuits.  Vary the number of sample points to see the
          effect.  Try setting the TStop time much larger than the
          lowest natural frequency in your circuit.  Try setting the
          TStop time shorter than the highest natural frequency in the
          circuit.  By trying these things you will quickly get a feel
          for their effect and understand more than you can by just
          reading.
          PC-ECAP Reference Manual                          page 33

          An Example Please!

          It's about time now to look at an example circuit.  We will
          analyze a simple RC low-pass filter.  The circuit is shown
          below.


                        1        1.59K                 2
                         ------/\/\/\/\------*---------
                                             |
                                             |
               input                      ___|___  .1uf      output
                                          _______
                                             |
                                             |
                                          0  |
                         --------------------*----------


          This circuit has 3 nodes and they have been numbered.
          Notice that we have numbered the common node between the
          input and the output as node 0.  This is required.

          The next thing to do is to describe the circuit to PC-ECAP
          so that it will know just what is connected to what and the
          component values associated with each part.  The next two
          lines will completely describe this circuit:

               R 1 2 1.59K
               C 2 0 .1UF

          The first line says to PC-ECAP that a resistor is connected
          between nodes 1 and 2 and has a value of 1.59K (notice that
          you don't have to enter 1590 for the resistor value, PC-ECAP
          understands what "K" means).

          The second line reads "a capacitor is connected between
          nodes 2 and 0 and has a value of .1uf".  Now all we have to
          tell PC-ECAP is where we want to put the input signal, where
          we want to look for the output and what frequency range we
          want to cover.  This is done with the PLOT statement.  For
          this circuit we want node 1 to be our input and node 2 to be
          our output.  Also we want to sweep the input frequency from
          100Hz to 10KHz in a logarithmic fashion.  The next line will
          tell PC-ECAP all this.

               PLOT 1 2 100 10KHZ LOG

          On your distribution disk (or in the archive file if you got
          this program from a BBS) you will find EXAMPLE1.DAT.  This
          file contains the circuit description for this circuit.
          PC-ECAP Reference Manual                          page 34

          If you haven't started PC-ECAP yet do so now.  From the
          main menu choose the "Select input file" selection.  Select
          EXAMPLE1.DAT as your input file.  Next from the main menu
          choose "Edit input file".  The editor will load EXAMPLE1.DAT
          and you will see the following:


          ; Example1.dat - RC low-pass filter with a cutoff frequency
          ;                 of 1 KHz.

          R 1 2 1.59k
          C 2 0 .1UF
          PLOT 1 2 100 10KHZ LOG

          This circuit description tells PC-ECAP all that it needs to
          know about this circuit and how you want to analyze it.

          Press ESC to get back to the main menu and now choose
          "Analyze circuit".  The analysis will begin and you will see
          the results as the program progresses.  When the analysis is
          complete, the results will be plotted on your display.
          First you will see a plot of Magnitude vs. Frequency.  If
          you press any key other than ESC you will get a plot of
          Phase vs. Frequency.  Pressing any key (other than ESC)
          again will show you Magnitude again.  If you have an EGA
          with 256K of memory or a Hercules or VGA card, both pages of
          graphics memory will be used and the change from Phase to
          Magnitude and back will be instantaneous.


          An Example of Transient Analysis

          EXAMPLE2.DAT is the same circuit as EXAMPLE1.DAT.  But this
          time we're going to run a transient analysis.  We'll pick a
          Stop time of 3 ms and a 1.5 ms Pulse for the input.  The
          input pulse will be delayed .1 ms to show the leading edge
          better.  This is the circuit listing:

          ; Example2.dat - RC low-pass filter with cutoff frequency of
          ;   1 KHz.  This example shows how to analyze a circuit's
          ;   transient response.

          R 1 2 1.59K
          C 2 0 .1UF
          PLOT 1 2 .1MS 3MS TRAN PULSE 1.5MS

          That's all there is to it.  Select EXAMPLE2.DAT and run an
          analysis on it.  Try varying the Stop time or the Pulse
          width.
          PC-ECAP Reference Manual                          page 35

          Another Example

          We have included a few other sample circuits with PC-ECAP.
          EXAMPLE3.DAT is a 75 ohm high-pass filter that can be used
          to reject television interference.  EXAMPLE4.DAT is a
          band-pass filter for use as a modem receive filter.  This
          example shows how group delay is calculated.  EXAMPLE6.DAT
          is an LC low-pass filer for which input impedance is
          calculated.  EXAMPLE7.DAT is an example of the calculation
          of return loss.  EXAMPLE8.DAT is an LC band-pass filter for
          which VSWR is calculated.  EXAMPLE9.DAT is an LC low-pass
          filter with a Square wave as input (for another example of
          transient analysis).  If you'd like, take a look at them and
          run an analysis.  You may want to draw them on a piece of
          paper first to really see what you are doing.
          PC-ECAP Reference Manual                          page 36

          For our last example we're going to take a look at
          EXAMPLE5.DAT.  This circuit is a single stage transistor
          amplifier made with a 2N3904 NPN transistor.  We will
          demonstrate the use of the "Model Maker" that is part of the
          full screen editor.  Here's the circuit:


                                                   +10 volts
                                             0  |
                                                \   R4
                                                /   470 ohms
                                                \
                                                /
                                       R3       |
                                      8.2K      |  3
                                  +--\/\/\/\----*---------
                                  |             |         output
                                  |            /
                        R1        |         | /
              1        270 ohms   |   2     |/       2N3904
                -------/\/\/\/\---*---------|
                                  |         |\
          input              R2   \         | \
                            1.2K  /           _\/
                                  \             |
                                  /             |
                                  |   0         |
                ------------------*-------------*---------



          As you can see the first thing you need to do is to number
          the nodes.  Please take a look at the top of R4.  This end
          of the resistor connects to the +10 supply voltage but we
          have numbered it as node 0.  This is an important point.
          Any node that has a DC voltage connection should always be
          connected to ground.  For the sake of an AC analysis, any DC
          voltage source is the same thing as ground.

          Now that we have numbered the nodes, we can describe the
          circuit:

               R1 1 2 270
               R2 2 0 1.2K
               R3 2 3 8.2K
               R4 3 0 470

          Alright, now we are ready for the NPN transistor.  The
          transistor that we are using is a 2N3904.  We could use a
          simple one line description for this transistor, but that
          wouldn't show what happens to the transistor at high
          frequencies.  What we need is a more sophisticated
          transistor model.  One that will change its characteristics
          as the frequency changes like a real transistor.
          PC-ECAP Reference Manual                          page 37

          PC-ECAP has the capability to create just such a model.  But
          first you need to know some information about the transistor
          that you want to model.  This is what is required:


          DC collector current -

                         For this circuit about 10 milli-amps flows
                         from the collector to emitter.

          Transistor current gain -

                         At 10 ma. this is a minimum of 100.  This is
                         the same as Beta (the current gain at DC).

          Transistor Gain-bandwidth product -

                         For the 2N3904 with a collector current of 10
                         ma. this is 300 MHz minimum.  This is also
                         known as Ft.

          Common base output capacitance -

                         This is just the capacitance from the base to
                         the collector.  For the 2N3904 it is 4 pf
                         maximum.


          Now that we have the required information we can make a
          transistor model.  Please note that it doesn't matter for an
          AC analysis whether the transistor is NPN or PNP.

          From the editor press F2.  This will start the Model Maker
          function.  A window will appear and ask first for the node
          numbers for base, emitter and collector.  You would just
          enter 2, 0, and 3.  Then you will be asked for the
          information mentioned above.  After answering all the
          questions your model will be created and inserted into your
          circuit description on the line following the cursor.

          For this circuit we might want to know just how good a
          frequency response we have, so let's sweep a frequency range
          of 1 KHz to 100 MHz.  And let's do it logarithmically.  With
          node 1 as the input and node 3 as the output, this line
          should make PC-ECAP do what we want:

                    P 1 3 1KHZ 100MEG LOG

          As you might notice, PLOT can be abbreviated to P.

          That's all there is to it.  Run an analysis and see what
          kind of amplifier we have.  You should also try changing
          some component values to see what happens.  What happens if
          you decrease R1?  Or increase it?
          PC-ECAP Reference Manual                          page 38

          Models

          The circuit models that PC-ECAP uses for Transformers,
          Bipolar transistors, FET's, Operational Amplifiers, and
          Transconductance Amplifiers are ideal models.  If you
          desire, you can easily create models that are more complex.

          For Bipolar transistors if your need a better model just use
          the "Model Maker" feature in the editor.  As previously
          discussed, a Hybrid-Pi transistor model will be created and
          inserted into your circuit description.

          For the transformer, the addition of two inductors will make
          a transformer that is quite "real".  You can add an inductor
          in parallel with the primary to model the transformer's
          magnetizing inductance.  This inductor should be equal to
          the transformer's primary inductance.  The transformer's
          manufacturer can supply the inductor value for this or you
          can measure it yourself (the secondary should be open for
          this test).  A second inductor can be added in series with
          the primary winding (and the inductor paralleling the
          primary).  This inductor will model the transformer's
          "leakage" inductance.  This inductance is due to the
          magnetic field that does not couple the primary and
          secondary windings.  Again, the transformer's manufacturer
          can supply this or you can measure it (measure the primary
          inductance as before, but this time short out the
          secondary).  By adding these two inductors, you will create
          a transformer that has a finite bandwidth.  The parallel
          inductor affects the low frequencies and the series inductor
          will affect the high frequencies.

          For FET's, the addition of a capacitor to model the gate to
          source capacitance and a second one to model the gate to
          drain capacitance will improve accuracy at high frequencies.
          You can get the appropriate values from your transistor's
          data sheet.  Also the Siliconix Low Power Discretes data
          book is an excellent source for more information on this.

          For FET's:     Cgs = Ciss - Cgd = Ciss - Crss

                         Cgd = Crss

          Operational Amplifiers today are usually frequency
          compensated internally.  Most of the time a method called
          "dominant pole compensation" is used.  This method inserts a
          pole in the opamp's frequency response at a very low
          frequency.  This pole will dominate the response (hence the
          name) and roll off at a 20 db/decade rate.  The opamp model
          that PC-ECAP uses is not frequency dependent.  The open-loop
          gain that you ask for is the gain that you will get for all
          frequencies.  It's not that difficult to make an opamp model
          that will decrease its gain as frequency increases.  Such a
          model is included on your disk as OPAMPMOD.DAT.  Please take
          a look at it.
          PC-ECAP Reference Manual                          page 39

          References for Modeling

          Although we have tried to give you some useful information
          to use for modeling circuit elements, a full treatment of
          the subject is beyond the scope of this manual.  For those
          of you who are interested, a good college library should
          have several books that might help.  Two references that may
          be more readily available for many people are:

          "National Semiconductor Linear Applications Handbook" from

          National Semiconductor Corporation
          2900 Semiconductor Drive
          Santa Clara, CA 95052-8090

          This handbook has an excellent paper entitled "The
          Monolithic Operational Amplifier: A Tutorial Study".  This
          paper tells you just about everything that you would want to
          know about the inner workings of opamps.

          A good reference for FET's in general is:

          "Siliconix Low Power Discretes Data Book" by

          Siliconix Incorporated
          2201 Laurelwood Rd.
          Santa Clara, CA 95054-1516

          They have several interesting application notes on the use
          of FET's.


          Parting Comments

          A considerable amount of time and effort was expended to
          develop PC-ECAP.  We sincerely hope that you feel it was all
          worth it.  We want you to know that we don't intend to stop
          here.  We have even more ideas for enhancements we would
          like to add in future releases.  But it is you that will
          make it possible.  By registering your copy of PC-ECAP, you
          will help make the possible into reality.  Thanks for your
          support.
          PC-ECAP Reference Manual                          page 40

          Revision History

          Version 3.02 - 4/14/98
          European format may now be specified for most scale factors.
          Analysis speed has been improved a bit more.  Contact and
          ordering information has been updated to include our web
          site and new address.

          Version 3.01 - 1/24/94
          Some Super VGA cards using Western Digital 90C31 or 90C31
          chips have a bug in their video BIOS.  This causes PC-ECAP
          to hang on program startup.  A work around has been added
          to solve this problem.  Added /v and /vm switches to force
          640x480 graphics modes.  Also added the tab key to editor.

          Version 3.00 - 11/01/93
          Added Transient analysis calculations.  Added transmission
          lines as circuit elements.  Added zoom and print features to
          plot screen.  Added support for HP DeskJets.  Improved
          support for HP LaserJet Series I.  Now displays more digits
          of frequency when plotting narrow band high frequency
          graphs.  Analysis routine is now 40-100% faster.

          Version 2.10a - 8/18/93
          In some rare situations, graphs would autoscale improperly.
          Fixed.

          Version 2.10 - 11/09/92
          Now handles circuits with up to 90 nodes.  Added option to
          print only circuit description and graphs.  Negative
          inductor values are now accepted.  Changed listing format
          for frequencies of 10 GHz and above.  Added network (LAN)
          support.  Fixed "border flash" when switching from graphics
          to text mode on some CGA cards.  Added table of contents to
          manual.

          Version 2.01 - 2/03/92
          Improved syntax checking on the circuit description files.
          More input errors are spotted and flagged.

          Version 2.00 - 10/14/91
          Added group delay, impedance, VSWR and return loss
          calculations.  Now has full support for 24 pin printers.
          Now supports HP LaserJet.  Editor has been enhanced.
          Analysis routine is now twice as fast as previous versions.
          Added AT&T and MCGA support.  Added support for a math
          coprocessor.  European format for element values now
          accepted.  Improved error checking on circuit description
          files.  International time and date on printouts now
          supported.  Numbers are now stored in IEEE binary format.
          No longer supports "non-compatible" video.  Now requires
          384K of system memory.

          Version 1.11 - 11/23/90
          Added the filename to the headers and plot sheet of the
          printout.  Negative resistance values are now accepted.
          Fixed bug in hard copy plotting routine - plot would display
          spurious points if the plot exceeded the maximum range.
          Fixed bug in analysis routine; Occasionally, a circuit with
          a very wide range of reactive component values could create
          an internal numeric overflow.
          PC-ECAP Reference Manual                          page 41

          Version 1.10 - 9/14/90
          Added the option of 35 sample points to the select number of
          sample points menu.  Greatly increased the number of plot
          ranges available when displaying results.  Magnitude now
          spans .1 db/div to 80 db/div and Phase now spans 22.5
          degrees/div to 720 degrees/div.

          Version 1.02 - 1/30/90
          First release widely distributed.
          PC-ECAP Reference Manual                          page 42

                        Appendix A - Command Line Switches


          PC-ECAP will automatically determine the type of video
          display adapter that your computer uses and will set itself
          accordingly.  There are a few situations where it is not
          possible to accurately determine the adapter type.  For
          example, if a monochrome monitor is used with a CGA card,
          the program has no way of knowing that.  Also, there are
          some advanced EGA cards that will change their display mode
          to match a given program.  Since PC-ECAP is trying to change
          its mode to match the video adapter, there can be no
          guarantee as to what you will actually wind up with.

          In order to accommodate these situations (as well as others
          that may be unforeseen at this time) PC-ECAP has a series of
          optional command line switches that can be used to set the
          video display mode.

          To start PC-ECAP with a command line option, type this at
          the DOS prompt:

                    ECAP    [ option ]

          Where "option" is one of the following:

               /H        Hercules Monochrome Graphics card (or
                         compatible).

               /C        Color/Graphics Adapter with color monitor.

               /CM       Color/Graphics Adapter with monochrome
                         monitor.  For use with Compaq monochrome
                         display or computers having LCD displays.

               /E        Enhanced Graphics Adapter with EGA monitor.

               /EC       Enhanced Graphics Adapter with CGA monitor.

               /EM       Enhanced Graphics Adapter with monochrome
                         monitor.

               /MC       Multi-Color Graphics Array.

               /M        Monochrome Display Adapter.

               /A        AT&T or Olivetti video adapter with color
                         monitor.

               /AM       AT&T or Olivetti video adapter with
                         monochrome monitor.  May also be useful for
                         some Laptop computers.

               /V        VGA Adapter with color monitor.  640x480

               /VM       VGA Adapter with monochrome monitor.  640x480
          PC-ECAP Reference Manual                          page 43

                           Appendix B - Error Messages


          ABORT -- Bad circuit description

               The PLOT statement must be the last line of your
               circuit description.  You have entered additional
               circuit elements after the PLOT statement.  Move these.


          ABORT -- Blinking nodes have been skipped

               You have skipped over one or more nodes in your circuit
               description.  Node numbers must begin at 0, and be
               numbered consecutively.


          ABORT -- Blinking nodes have less than two components

               Your circuit description has one or more "dangling"
               components.  All nodes (other than the input) must have
               at least two components attached.


          ABORT -- Insufficient memory for operation

               PC-ECAP makes extensive use of dynamic memory.  That
               is, memory that it allocates only when needed.
               Although this makes for very efficient memory usage,
               peak memory requirements can not be known up front.
               Your only choice here is to do without the feature
               that gave you this error or get more RAM memory for
               your computer.  PC-ECAP can use Upper Memory Blocks
               (UMB's) if you have DOS 5 or greater.  Be sure you
               have UMB support enabled.


          ABORT -- Invalid circuit element

               You have an unknown circuit element in your circuit
               description file.  Valid lines must be either blank,
               begin with a semicolon ";" (if a comment), or begin
               with one of the letters of a circuit element.


          ABORT -- Invalid node number

               You have a circuit element that has one or more node
               numbers that is not an integer, is negative or is
               greater than 89.
          PC-ECAP Reference Manual                          page 44

          ABORT -- Invalid reference impedance

               You have asked to compute the VSWR or return loss for a
               circuit, but have not specified an impedance to
               reference these calculations to.  Or your impedance is
               negative or zero.  Must be a positive value.


          ABORT -- Too many circuit nodes

               You have 1 or more circuit nodes with a number greater
               than 89, either because you actually have a circuit
               with more than 90 nodes or you have made a typo and
               have inadvertently skipped some.


          ABORT -- Too many circuit elements

               You have exceeded the limit of 1000 circuit elements.
               R, C, L, Transmission lines, Fet's and Transconductance
               amplifiers each count as one circuit element.  OpAmps
               and Bipolar transistors count as two.  Transformers
               count as four.


          ABORT -- Too many transmission lines

               You have more than 64 transmission lines in your
               circuit.


          ABORT -- Unknown parameter specified

               You have listed a parameter that is unrecognized and
               unexpected.  Recheck the syntax of the line displayed.


          ABORT -- Unknown sweep type

               You have specified a sweep type that is something other
               than LINear, LOGarithmic or TRANsient (may be
               abbreviated to the letters shown capitalized).


          ABORT -- Wave type not specified

               You have asked for a transient analysis, but have
               omitted the type of waveform to be used as input.
          PC-ECAP Reference Manual                          page 45

          CAUTION! Conflicting transistor parameters supplied

               The data that you have entered for your transistor
               doesn't make any sense.  For example - you may have
               said that your transistor has a very high cutoff
               frequency and then specified a huge base to collector
               capacitance.  Or you may have specified a very low
               collector current and a high cutoff frequency.  Things
               that contradict each other.  Recheck your data and
               change if necessary.


          ECAPHERC.DRV is not found

               You have a Hercules or Hercules compatible graphics
               card, and the required driver ECAPHERC.DRV is missing.
               This driver is needed to display text when PC-ECAP is
               in graphics mode.  If you have DOS version 3.0 or
               greater, PC-ECAP will look for this file in the same
               directory that contains ECAP.EXE.  This may be
               different than the directory that contains your circuit
               files.  Otherwise, ECAP.EXE and ECAPHERC.DRV should be
               in the current directory.


          File is currently being used by someone else

               You can get this message when you are running PC-ECAP
               on a network or multi-user system and you attempt to
               access a file that is already in use.  Wait until the
               file is available or pick a different file.


          Floating point math error -

               It should not be possible to get this error.  If it has
               occurred, please send us a complete description of what
               you did to get it, so that we may look into the
               problem.


          Input File Size Limit Reached

               PC-ECAP allocates a 500 line buffer for its editor.
               Your circuit description file has exceeded this amount.
               The only way this should happen is if you have filled
               your circuit description file with comments or other
               nonessential information.  Remove the extra data.


          Insufficient disk space

               Well, what can we say, your disk is full.  Delete those
               files that you really don't need or get a bigger disk.
          PC-ECAP Reference Manual                          page 46

          LPT1, LPT2 or LPT3 is not ready

               You requested PC-ECAP to print something but your
               printer isn't ready.  Check to see that your printer's
               power is turned on.  Also check to see if your
               printer's cable is connected.  You will also get this
               message if you try to print on a printer that does not
               exist.


          No files found.  Enter name of new file.

               When you tried to select an input file, PC-ECAP didn't
               find any that had the extension ".DAT".  If you
               actually believe that there should be circuit
               description files in you current directory, quit
               PC-ECAP and check to see if you are in the correct
               directory.


          Not enough space for . . .

               You are out of memory and PC-ECAP is unable to load.
               Remove any TSR programs from memory or get more memory
               for your computer.


          Please create this file or select another

               You have asked for an analysis of a circuit that does
               not exist.  Use the text editor to create a circuit
               description file for your circuit.


          Please run an analysis or select another

               You have asked to see the results of a circuit that you
               haven't analyzed yet.  Run an analysis.


          Unable to delete "filename"

               You tried to delete a file that was most likely marked
               as Read Only.  Check to see if this is the case and
               change the file's attribute if necessary.


          You have enough memory to analyze circuits with
               up to ## nodes.

               If your computer has less than 450K of free memory
               available, you will see this message when you start
               PC-ECAP.  The program is giving an estimate of the
               maximum circuit size you can analyze based on the
               amount of memory in your system.
          PC-ECAP Reference Manual                          page 47

          Your copy of PC-ECAP has been damaged!

               Someone or something (another program perhaps) has
               changed your copy of ECAP.EXE.  PC-ECAP checks itself
               every time it runs and this check has failed.
               Reinstall the program.
          PC-ECAP Reference Manual                          page 48

                                   Appendix C
                    PC-ECAP to Lotus 1-2-3 file conversion


          Included with the REGISTERED version of PC-ECAP is the
          utility program ECAP2WKS.  This program can be used to
          convert PC-ECAP ".OUT" files into Lotus 1-2-3 compatible
          spreadsheets.  This can be very useful if you want to do
          additional operations on your data, such as normalizing
          circuit gain at a particular frequency or plotting several
          quantities on the same graph.

          These PC-ECAP spreadsheets can be used with just about all
          of the popular spreadsheet programs such as Lotus 1-2-3,
          Quattro Pro, Microsoft Excel and the excellent shareware
          program AS-EASY-AS.

          To convert a file just type:


               ECAP2WKS  filename.out


          Filename.out should of course be the name of the PC-ECAP
          file that you want to convert.  If you don't specify a file
          extension, ".OUT" will be assumed.  As an option, you can
          also specify the name of the converted ".WKS" file.  To do
          this, just add its name after "filename.out".  The ".WKS"
          file extension is optional:


               ECAP2WKS  filename.out   filename.wks


          ECAP2WKS will accept wildcards.  For example, to convert all
          files beginning with "BAND", such as "BAND_ONE", "BAND_TWO",
          etc., type:


               ECAP2WKS  band*.out


          And finally, you may also specify full drive and path
          specifications along with the filenames.  For example:


               ECAP2WKS  D:\ecap\lowpass.out  C:\lotus\123files\


          will convert "LOWPASS.OUT" to "LOWPASS.WKS" and place it in
          the \LOTUS\123FILES subdirectory on drive C:.

          ECAP2WKS checks to see if the file specified is really a
          PC-ECAP ".OUT" file before attempting a conversion.
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