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P C - E C A P Version 3.00 Program Reference Manual Copyright (c) 1990-93 by Peter Volpa All Rights Reserved _______ ____|__ | (R) --| | |------------------- | ____|__ | Association of | | |_| Shareware |__| o | Professionals -----| | |--------------------- |___|___| MEMBER Peter Volpa Circuit Systems 418 Church Road Sicklerville, NJ 08081-1727 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 . . . . . . . . . . 41 Appendix B - Error Messages . . . . . . . . . . . . . 42 Appendix C - PC-ECAP to Lotus 1-2-3 file conversion . 47 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 9/24 pin, HP LaserJet and HP DeskJet compatible printers. * 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 registrations come in two forms. The first, registration only, costs $89 (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. We also offer PC-ECAP with a printed manual. For $99 (plus $4.00 shipping and handling) we will send you the latest registered version of PC-ECAP along with a professionally printed bound manual. 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. 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 418 Church Road (609) 875-5433 Sicklerville, NJ 08081-1727 12 - 10 PM EST Questions may also be sent by Email on CompuServe to 72202,3043. I check for mail only about once a week, so it might be just as quick to write if you live in the U.S.A. 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) 2424-PsL or (713) 524-6394. You may also FAX to (713) 524-6398 or CompuServe to 71355,470 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) 875-5433. All credit card orders will be charged $4 for Shipping and Handling. 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 545 Grover Road, Muskegon MI 49442-9427 or send a Compuserve message via CompuServe Mail to ASP Ombudsman 70007,3536. The OMB may be contacted by FAX by sending to the ASP FAX number: (616) 788-2765. 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, XT, AT, PS/2 or compatible. * 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. 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 another 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 3.00 - 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 certain 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. 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 41 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. PC-ECAP Reference Manual page 42 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 43 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 44 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 45 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 your 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 46 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 47 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.