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P C - E C A P Version 1.10 Program Reference Manual Copyright (c) 1990 by Peter Volpa All Rights Reserved _______ ____|__ | (tm) --| | |------------------- | ____|__ | Association of | | |_| Shareware |__| o | Professionals -----| | |--------------------- |___|___| MEMBER Peter Volpa Circuit Systems 418 Church Road Sicklerville, NJ 08081-1727 page 1 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 4-digit 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 (c) 1990 Circuit Systems page 2 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 $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. We also offer PC-ECAP with a printed manual. For $79 (plus $3.00 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 7% sales tax. Educational institutions may apply a 35% discount to all prices. PLEASE include your educational institution letterhead (with your title) when you order. 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 Circuit Systems 418 Church Road Sicklerville, NJ 08081-1727 PC-ECAP Reference Manual (c) 1990 Circuit Systems page 3 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 is a registered trademark 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. 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 P.O. Box 5786, Bellevue, WA 98006 or send a Compuserve message via easyplex to ASP Ombudsman 70007,3536. PC-ECAP Reference Manual (c) 1990 Circuit Systems page 4 Introduction PC-ECAP is an easy to use AC circuit analysis program which analyzes circuits consisting of resistors, capacitors, inductors, transformers, 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 phase response, a high resolution display plotter that supports all common graphics adapters and a high resolution plotter for IBM/Epson compatible printers. Features: * Completely menu driven - very easy to use. * Can analyze circuits with up to 40 nodes - no limit on the number of 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 and even the Monochrome Display Adapter. * All calculations are done in double precision - 14 digits of BCD. * High resolution plots on IBM/Epson 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. * Does not need a numeric coprocessor. PC-ECAP Reference Manual (c) 1990 Circuit Systems page 5 System Requirements: * IBM PC, XT, AT, PS/2 or compatible. * PC or MS-DOS 2.0 or later. * One floppy disk drive. * 182K of free memory - that is, 182K in addition to the operating system and any resident programs that you may have loaded. * A CGA, EGA, VGA or Hercules compatible 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 compatible printer, if hard copy is desired. Most printers used with IBM and IBM compatible computers support this standard. Be sure "IBM" mode is selected (usually by means of a dip switch). PC-ECAP Reference Manual (c) 1990 Circuit Systems 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. All 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. That's all. It is strictly for your convenience. The default "from" drive is drive A: and the default "to" drive is drive C:. These may be changed to any other drives 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: INSTALL Follow the directions and before you know it, you will have PC-ECAP on your hard drive. PC-ECAP Reference Manual (c) 1990 Circuit Systems 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 (c) 1990 Circuit Systems page 8 Getting Started PC-ECAP is started by typing the following command at the DOS prompt: ECAP [ options ] The optional command line switches should not be needed by 99% of computers, and therefore are covered separately in appendix A. 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. 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. PC-ECAP Reference Manual (c) 1990 Circuit Systems page 9 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. Cntrl Home - move to the beginning of the file. Cntrl 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. 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. PC-ECAP Reference Manual (c) 1990 Circuit Systems page 10 In addition to these special keys, five function keys have special meaning. 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. 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). PC-ECAP Reference Manual (c) 1990 Circuit Systems page 11 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. 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. Leaving The Editor When you are finished with your editing, press the ESC key. If you have made any changes to the file, you will be asked, "Save Changes (Y/N or <CR> for Yes)?". Answer "Y" to save all changes, or "N" to ignore all changes. A carriage return will save all changes. PC-ECAP Reference Manual (c) 1990 Circuit Systems page 12 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 magnitude and phase response at the selected output node. The input signal is from an ideal AC 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 frequencies in the specified input range. The number of frequencies within the input range that PC-ECAP will subject your circuit to, is controlled 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. As PC-ECAP progresses, it will display magnitude and phase results on the screen. 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". 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 MDA 80 x 25 Pressing any key other than ESC will toggle between the display of "Magnitude vs. Frequency" and "Phase vs. Frequency". Pressing ESC will return to the main menu. PC-ECAP Reference Manual (c) 1990 Circuit Systems page 13 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 ESC will toggle between the magnitude and phase displays. Pressing ESC will return you to the tabular listing of the data. Press ESC again to return to the main menu. Output to printer This choice 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". In either case the output will consist of a listing of the circuit description at the time of analysis, a tabular listing of the analysis results, and high resolution plots of Magnitude and Phase vs. frequency. It is necessary to have a printer that is IBM/Epson compatible if printed output is desired. Most printers used with IBM compatible computers support this standard, although in a few cases it may be necessary to select this mode by means of a switch on the printer. PC-ECAP Reference Manual (c) 1990 Circuit Systems page 14 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 and LPT1 selected as the output destination. Both of these may be changed by means of this menu. Change the number of sample points When an analysis is performed, the desired frequency 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 magnitude or phase. You may also want to increase the number of points if you analyze circuits over a very wide frequency 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). 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 (c) 1990 Circuit Systems page 15 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 40 nodes but no limit on the number of components. 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 15 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. PC-ECAP Reference Manual (c) 1990 Circuit Systems page 16 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 (c) 1990 Circuit Systems page 17 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 (c) 1990 Circuit Systems page 18 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. PC-ECAP Reference Manual (c) 1990 Circuit Systems page 19 Specifying 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 magnitude and phase response at the selected output node. 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 and the sweep mode (linear or logarithmic). This is the format for the PLOT statement: PLOT NI NO Start-frequency Stop-frequency Plot-mode 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. As an example, 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. Also lets sweep this range logarithmically. This PLOT statement will specify all this: PLOT 2 5 100HZ 10KHZ LOG PC-ECAP Reference Manual (c) 1990 Circuit Systems page 20 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 1500 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 (c) 1990 Circuit Systems page 21 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. Another Example We have included a few other sample circuits with PC-ECAP. EXAMPLE2.DAT is a 75 ohm high-pass filter that can be used to reject television interference. EXAMPLE3.DAT is a band-pass filter for use as a modem receive filter. 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 (c) 1990 Circuit Systems page 22 For our last example we're going to take a look at EXAMPLE4.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 (c) 1990 Circuit Systems page 23 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 (c) 1990 Circuit Systems page 24 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 dominant 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 (c) 1990 Circuit Systems page 25 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 several ideas for enhancements that 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. Revision History Version 1.10 - 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 - first release widely distributed. PC-ECAP Reference Manual (c) 1990 Circuit Systems page 26 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. /M Monochrome Display Adapter. /N Non-compatible video. PC-ECAP normally writes directly to video RAM for the fastest possible screen display. If the /N option is specified, all screen writes will go through the BIOS. Also, any on screen plotting will be done using character graphics. Use this mode only if no other mode works on your machine. PC-ECAP Reference Manual (c) 1990 Circuit Systems page 27 Appendix B - Error Messages ABORT -- Too many circuit nodes You have 1 or more circuit nodes with a number greater than 40, either because you actually have a circuit with more than 40 nodes or you have made a typo and have inadvertently skipped some. 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. HERC.DRV is not found You have a Hercules or Hercules compatible graphics card, and the required driver HERC.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.COM. This may be different than the directory that contains your circuit files. Otherwise, ECAP.COM and HERC.DRV should be in the current directory. Input File Size Limit Reached PC-ECAP allocates a 4K buffer for its text 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 none essential information. Remove the extra data. If you really believe that 4K is insufficient, let us know. 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 (c) 1990 Circuit Systems page 28 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. 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. Your copy of PC-ECAP has been illegally modified! Someone or something (another program perhaps) has changed your copy of ECAP.COM. PC-ECAP checks itself every time it runs and this check has failed. Reinstall the program. PC-ECAP Reference Manual (c) 1990 Circuit Systems