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ACIRAN V1.3 for Windows Linear AC Circuits Analysis Introduction. This Help file is a small subset of the printed manual supplied to registered users. ACIRAN is a Linear AC Circuit Analysis Program designed to ease small signal ac analysis of active and passive circuits. ACIRAN can handle Resistors, Capacitors, Inductors, Transformers(Ideal), Fets, Transistors, Operational Amplifiers, Transmission Lines, and Voltage Controlled Current Sources. To save time and ease design a number of Fet,Opamp and Transistor model parameters have been supplied. More complex models can be built up using passive components and Voltage Controlled Current sources. Installation. ACIRAN V1.3 was created using the Turbo Pascal for Windows Compiler (V 1.0) and is able to support co-processors, if you machine has a floating point chip this is detected by ACIRAN and used for all calculations, if you do not have a co-processor, it is simulated by software. Before using ACIRAN first make a backup copy on another disk, then put the original in a safe place. Create a working directory on your hard disk, and create a new group, e.g. CAD to hold Aciran, and install its icon. Getting Started. The main menu offers the following selection: File Edit Config Data Analyse Results Graph Help These are explained below. File provides the following sub-menu New Open Save Save As Printer SetUp Exit New is used to enter a new circuit description to ACIRAN and as it clears any previous circuit from memory you should save any data that you have in memory first. You will be given a warning first. Open allows you to load a previously saved circuit for analysis or modification. Circuits are expected to have extension .CIR or .CTS (automatically appended by ACIRAN). You will be presented with a Filebox. Use the cursor keys or mouse to highlight the file you wish to load and then press return or click the OK button. Save allows you to save your circuit description to disk. If you are entering a large circuit then you should save it periodically. Save_As allows you to save your circuit under a new name, perhaps to save a diffenent version. Save_As will be called the first time a circuit is saved as it will not have an existing filename. Printer SetUp will allow you to configure your printer, e.g. select landscape or portrait mode. Exit will exit from ACIRAN and take you back to Windows. Any circuit description held in memory will be lost so make sure you have saved any data that you want to keep. ACIRAN will give a warning if you have not saved your circuit and have made changes. Edit allows you to make changes to the circuit description such as adding or deleting components and changing component values. Edit has its own sub-menu which will be described later. Config allows you to set up certain flags and to request additional circuit parameters such as impedance and return loss. This information is stored along with the circuit details in the files. The Config dialog box will be descibed later. NetList allows you to inspect your circuit description by listing the components,their values and circuit connections. You can send the data to a printer by selecting Print from the system menu of the Netlist Window. Analyse instructs ACIRAN to analyse the circuit in memory. Logarithmic and Linear frequency sweeps are allowed. ACIRAN can also carry out Monte-Carlo analysis if component tolerances have been entered. Results offers the choice to Display or File. To view the results select Display, to obtain a hard copy of these result the Print option should be selected from the system menu of the Results Window. Results can also be stored in a text file for later use. Graph will plot various parameters such as Gain or phase against frequency. A Hard copy can be obtained by selecting Print from the system menu. To enter a circuit select New and enter a circuit name. This is for your benifit only, and appears in listings. Next you will see a dialog box of component types, use the normal selection methods to choose a component type. If the component type is Fet, Opamp or Transistor you will be asked if you wish to load model parameters from disk. If you select to do so you will be presented with another file selection box, to choose the component model. More about this later. An Example A number of examples are included on the disk. They will provide the most ideal method of learning ACIRAN. Enter the first one from the keyboard. The circuit is shown below: RC Filter. R1 node 1 ________ node 2 0---------| |---------------------o-------------------------0 -------- | 100 +/- 0.5% | ---- | | R2 | | | | 10 +/- 2% INPUT ---- OUTPUT | o node 3 | ----- 0.001uF +/- 10% _____ | C1 node 0 | 0_______________________________________o_________________________0 Select New from the File Menu. Enter the circuit description 'RC Filter' <cr>. When the Select component box is displayed,choose a resistor, and a form will appear on the screen ,you will be asked for the component identifier, enter 'R1' and press <TAB>.(Up to 5 characters can be entered for the component identifier). You will now move to the next input field, you will then be asked for the value of R1. Enter 100 <TAB>. You will then be asked for the tolerance in %. Enter 0.5 <TAB>. (The leading Zero is essential). Next you will be asked 'From Node', Enter 1 <TAB>, and then 'To node', Enter 2 <TAB>. The convention in ACIRAN is that the INPUT NODE is ALWAYS 1 and the GROUND NODE is ALWAYS 0. The OUTPUT NODE is variable(more about this later). Once you have completed the form you must press enter or click the OK button to exit and save you data. If you press Cancel the data will be ingored. You can move around the input form changing the information using the edit keys, until you are happy with what you have entered. Previously entered data that is presented and can be accepted by entering <cr>. Enter component R2 in the same way, it is not important which way round the passive component is connected. To enter C1 select Capacitor, and for the value enter 0.001u. the 'u' or 'U' at the end tell ACIRAN that the value is in microfarads. A number of multiplier options are allowed and upper or lower case can be interchanged in all cases except 'M' and 'm'. The multipliers accepted by ACIRAN are 'G' or 'g' Giga = x1E9 'M' Mega = x1E6 'K' or 'k' Kilo = x1E3 'm' milli = x1E-3 'U' or 'u' micro = x1E-6 'N' or 'n' nano = x1E-9 'P' or 'p' pico = x1E-12 These multipliers can be entered in a number of formats, eg 1k2, 1K2,1.2K 1200 12e2,12E2 and 1.2e3 are all acceptable and identical . Now that the circuit has been entered click Cancel in response to next component and you will be asked for the Output node. If you press <cr> without entering any data ACIRAN will assign the highest node used to the output node. In this circuit this is not the case and you must enter 2 <cr>. It is advisable to save your work and so as soon as the main menu returns press Alt-F for File then Alt-S for Save, or use the mouse. When asked for a file name enter any valid filename, remember to omit any file extension. You can check your circuit configuration by selecting NetList. The circuit listing is displayed. You can scroll through it using the scroll bar on the left of the window, or by pressing the up/down arrow keys or PageUp and PageDn keys. To Print the data select Print from the windows system menu. Check that the circuit connections are correct. If you do not wish to enter the circuit yourself you can load it from the disk by selecting Open at the main menu and loading 'EXAMPL1'. Now analyse the circuit by Selecting Analyse at the main menu. A frequency input form will appear, you must complete at least the first three entries, some have minimum default values already loaded. You can select Log or Linear sweep from the Config box, the default is Log. For the moment leave it as Log. Now enter the start frequency. Enter 100k and press <TAB>. Enter End frequency 100M (note capital 'M' for Megahertz). Finally enter the number of frequency steps, 10 <cr>. Leave the default number of passes as 1. Remember to press return or click OK once you are satisfied with the input data. If however you enter a number of Passes > 1 then ACIRAN will analyse your circuit that number of times, and on each pass it will vary the component values within the tolerance limits you specified for each component. This feature will be discussed later. ACIRAN will now analyse your circuit from 100 kilohertz to 100 megahertz in 10 Logarithmic steps. The Sweep mode selected will remain in force in future analysis unless you specifically change it. During Analysis the frequency sweep mode and range are displayed and a counter shows the percentage of the analysis completed. You Can abort the run by pressing Escape or clicking on the Cancel button. In either case you will get a message when the analysis is over. NOTE: Due to the numerically intensive nature of this program there may be a few seconds delay between the user aborting the run and Aciran recognising the abort message as it only checks the message queue once during each frequency pass. Select Results to see a table of results. Only Gain, Phase and Time Delay are shown by default, to see impedance or return loss you must check the boxes in the Config dialog box. To print select Print from system menu. Close the Results window, or minimize it. Select Graph and choose Magnitude. If your printer has Graphics capability you can obtain hard copies by selecting Print from the system menu of the Graph Window. The results for the RC Filters are shown below. Transmission Results for RC Filter - See Printed Manual Monte-Carlo Select Analyse again, but this time change the number of tolerance passes to 3 . It is not necessary to enter the Start and End frequencies again,or the number of steps, as ACIRAN will remember the previous values. You can however change any one of them (or all) if you wish. It is only necessary that you do not try to violate the input requirements (such as End frequency coming before Start frequency or a Log sweep on too small a frequency range). Keep the same frequency range and number of steps as before, and so enter <TAB> for each entry. This time during Analysis the window text shows the current Monte-Carlo pass being executed. At each pass the circuit is analysed using component values selected at random from within component tolerance limits. After analysis ACIRAN will output the results but this time the heading Upper Limit appears. This shows the upper limits reached during the Monte-Carlo passes. The Lower Limits are printed next. If you select Graph you will see not one but two graphs showing the spread of results obtained. This tolerance analysis lets you see how your circuit is likely to vary in performance due to component tolerances. In this example only 3 passes have been selected but in practice several hundred passes may be needed to give a representative picture. However this would take a lot longer and for large circuits the time can become excessive especially if there are a large number of frequencies. The largest number of passes is 32767. Editing Having entered the circuit (either from the keyboard or from disk), it is necessary to be able to modify it, in order to fine tune it. At the Main menu select modify, and a sub-menu appears with the following selection: Add Change Delete Replace Name Output and selection is made as before. Add allows you to extend your circuit provided there is enough room to do so. If you had previously saved your circuit (which you ought to do on a regular basis) it will allow you to carry on building your circuit from where you left off. Change allows you to change a components identifier, Reference, value, tolerance, and nodal connections. If you wish to change the component type delete the component and add a new one of the correct type. Delete allows the deletion of a component. Yoy will be asked to confirm that you wish to delete it. Name allows you to change the circuit identifier (or name) of the circuit. Output allows you to change the output node. If you wish you can look at nodes internal to the circuit to see their response. In some cases a circuit may have more than one output node, for example a circuit with one input and two complementary outputs, perhaps with a constant phase shift between the two outputs. How to Modify a Circuit Now change the value of C1 to shift the response of the RC Filter. If you have exited ACIRAN restart it and load 'EXAMPL1'. Select Edit and then select Change. You will be presented with a Pick list, select C1, by double clicking it, or selecting it then selecting OK. When asked for the value enter 0.002u <cr>. The new value will be assigned to C1. Quit Editing and display the circuit listing, check that C1 has the new value. Select Analyse and test the circuit response. If you have not exited from ACIRAN you will not have to re-enter the Start,End and frequency Step values,nor the Output node. From the output results (and graphs) you can see the effect of the circuit change. If you wish you can save this circuit, either as a new one under a new filename,or you can overwrite the old circuit description. Suppose for the sake of instruction it is decided that R2 should be changed from a resistor to an inductor, this would give a notch Filter. This can be done by first deleting R2 and then adding an inductor L1. Do this in two stages to show the effect on the circuit listing. From the main menu select Edit, and then Delete. Select R2 from the list. Select Add, Chose Inductor, Enter the component identity as 'L1', it's value as 0.33u (0.33 micro-henry), Tolerance 10, and its connections 'From node' 2,'To node' 3. Check the circuit listing. Re-Analyse the circuit and check that it is now a notch filter. Use the same frequency range. If you have not exited ACIRAN you need not re-enter this data. Now that you have changed the circuit you should give it a new name. Enter the Edit menu and select Name. Enter 'RLC Notch Filter' <cr>. You may wish to save your new circuit under a new filename. Select Save_As. Transmission Results for RLC - See Printed Manual How to Configure Aciran. ------------------------ At the Main menu select 'C' for Config, and a dialog box appears with the following selection: Format Polar or Cartesian checkbox Returnloss On or Off checkbox Impedance On or Off checkbox Sweep Logarithmic or Linear checkbox Tolerance On or Off checkbox Beep On or Off checkbox Generator Reference Impedance edit window Load Reference Impedance edit window Format allows you to select the format used for impedance results. A choice of Polar or Cartesian coordinates is available. Choice is made by pressing clicking on the relevant checkbox, the other box will be unchecked. IF you select Polar (this is the default setting) then impedance results will be output as a Magnitude and Phase angle. On the other hand if you select Cartesian then impedance results will be output as a Real and Imaginary part. Returnloss ReturnLoss is calculated with respect to the input and output referance impedances. The default is 100Mohm real for both input and output. This means that your circuit is analysed without taking into account the effect of realistic source and load impedances. You can change the Source and Load referance impedances to more practical values and Input and Output impedances will be calcuated taking these referances into account, or if you leave them unchanged you will get the open circuit input and output impedances without loading effects. Once you have changed the referance impedances they will remain changed until you load or enter a new circuit, or specifically alter them. ALL config options are saved along with the circuit data to save having to change it every time the circuit file is loaded. Impedance and ReturnLoss calculations are automatically performed, they are not displayed unless checked in the config box. The Graphs are available always. Once you have changed the referance impedances they will remain in effect until you load or enter a new circuit, or specifically alter them again. This will be illustrated later by an example. Sweep allows you to change the sweep mode (Logarithmic or Linear). If you start a New circuit the Sweep mode defaults to Logarithmic. This mode will remain in force until changed by means of the Config Sweep command. Tolerance simply toggles the Tolerance entries flag on and off. If, in order to save time you selected no tolerance entries for a circuit, and at a later date wanted to see the effect of tolerance on your circuit due to one or more components, you can turn on tolerance by means of this switch. All the components will originally have 0% tolerance but you can change this by using the Change feature. Beep allows you to turn off the warning beeps that are issued by ACIRAN should you not wish to disturb others. The only exception is the case where you are about to exit ACIRAN or load a new circuit, and have not saved your work. Generator This option allows you to set up the source referance impedance. You may enter values in the same format as that used for resistors (ie multipiers are accepted). Load This option allows you to set up the load referance impedance. You may enter values in the same format as that used for resistors (ie multipiers are accepted). Further Examples You have now covered most aspects of ACIRAN with the exception of MODELS. How to create your own MODELS using any wordprocessor is explained in the Appendix, for the moment simply examine how you can use the ones supplied on the disk. To do this look at some more examples which make use of MODELS. The next circuit (EXAMPL2 on the disk) uses a single transistor in a common emitter amplifier, and is shown below: Transistor Amplifier See Printed Manual Note that both power supply rails are numbered node zero. This is because as far as AC analysis is concerned the power supply is an AC short circuit, normally due to decoupling capacitors. You could add a DC Voltage Source which is included for compatibility with PSpice. The Voltage source will be treated as a short for AC Analysis purposes. Enter the circuit as shown. When you select component type Transistor you will be asked if you want to load model parameters, enter 'Y'. You will be presented with a filebox similar to the type used for loading circuit files, select a 'BC107'. How to add more models will be covered later. If you enter 'N' for loading a model file ACIRAN will assume that you are unable to supply a model file and will ask you for details of the transistor which must be entered from the keyboard. In either case once the Transistor parameters are loaded you will be presented with a Transistor Form, most of the details will be filled in if you loaded model parameters from disk (This is also true for FET and OPAMP) model files). You must enter a circuit identifier,(this is needed to select the component from a Pick List during subsequent edit operations), also for the Base, Collector, and Emitter node connections, and these should be entered with reference to the above circuit. The default collector current is 1mA, this can be altered once you have calculated the DC current. Analyse the circuit from 10 hertz to 10 Megahetrz in 10 Log steps. The resistor R5 is not needed by ACIRAN but was added so that the results of the ACIRAN analysis could be compared with the output from a proprietary Circuit Analysis package that runs on a Vax under VMS4.6. The results compared almost exactly at low frequencies and only at higher frequencies could any significant differance be spotted. This is due to the type of transistor model used by ACIRAN which is a simple model requiring only 3 nodes. A more precise model can be used which requires one extra node for each transistor, and the same circuit using just such a model is illustrated in EXAMPL3. Transistor Amplifier Results - See Printed Manual A Transistor can be modeled using the Hybrid PI model as show below: Hybrid PI Model See Printed Manual The three nodes B,C,E are the same as before,however an extra node b' is needed to model the Transistor base spreading resistance. The parameters shown can be calculated from manufactures test data and are dependant on the small signal 'h' parameters, the transition frequency FT, collector current and the transistor internode capacitances. In EXAMPL3 the BC107 transistor has been modeled in this way. Methods of calculating the Hybrid parameters can be found in the Appendix. The only new component type is the Voltage controlled Current Source 'gm'. The Source is a four terminal device which can be used to model all kinds of active devices such as Fets and Opamps. The From node is the current source,in this case the Collector, and the To node is the current drain. The + control node is the drive source for the current generator, here the Base, and the - control node is the drive sink, for a CE circuit it is the Emitter. Analyse EXAMPL3 over the same frequency range as EXAMPL2 and examine the differences. The rest of this manual will describe the circuit examples supplied on the disk. Each example was chosen to exhibit certain features of ACIRAN. All resistors are 1% and all capacitors 10% unless stated otherwise. EXAMPL4 This is a simple transformer coupled stage connecting a 50 ohm source to a 1k load. As ACIRAN references both Input and Output to ground it is necessary to connect the transformer primary and secondary windings to ground for analysis. In practice these connections could be omitted to provide DC isolation. In transformer coupled amplifier stages where the second stage is referenced to ground there is no problem and the transformer can be connected as normal. As stated before ACIRAN models Ideal transformers, whereas in reality transformers have winding resistance and inductance.These imperfections are modeled by adding resistors and inductors to the circuit as shown below. RP and RS are the primary and secondary DC winding resistances for the transformer. The inductors LP and LS simulate the transformer inductances. The primary has 1000 turns and the secondary 1080, therefore as a ratio to one is required, enter 1.080 into the transformer form at the ratio field. Analyse the circuit from 20 to 20k in 10 Logarithmic steps. Transformer Coupled Stage See Printed Manual Transformer Stage Results - Stage See Printed Manual EXAMPL5 This is an Elliptic-function Bandpass Filter. The filter is to work into a 10K Load from a 10K Source. Select Config and check ReturnLoss. You should then change the source and Load referance impedances,Zin and Zout, the default is 100Mohms real. You can change these to 10K real and 0 ohms imaginary. Quit Config and analyse the filter. The filter has a passband from approximately 15khz to 20khz. Using a Linear sweep examine the response from 12khz to 24khz in 10 steps. Notice that the filter response changes sharply below 15khz and above 20khz. Now examine the response from 15khz to 20 khz in 40 steps, in order to see how much ripple exists in the passband. Elliptic-Function Bandpass filter See Printed Manual Transmission Results for Elliptic BandPass Filter - See Printed Manual EXAMPL6 This is a VHF/Video amplifier using an FET.The circuit is show below: Again note that both power rails are at node 0. Analyse the circuit from 1M to 200M on a Log sweep. Fet Amplifier See Printed Manual Fet Amplifier Results - See Printed Manual EXAMPL7 This example is of a Twin-T notch filter and illustrates the use of an Opamp. The circuit is shown below: Twin-T Filter See Printed Manual Analyse the circuit from 10 hertz to 2k hertz in 10 Linear steps. Note that the notch frequency occurs at about 1khz. Twin-T Filter Results - See Printed Manual EXAMPL8 This is a Single Bandpass Filter section. It has a response curve which is the inverse of exampl7. It is designed to have a centre frequency of 3.6khz and a 3dB bandwidth of 60Hz. Analyse the circuit on a Linear sweep from 3.0khz to 4.5khz in 10 steps. Note that R6 is variable in order that the circuit response can be finely adjusted.Experiment by changing the value of R6. Single Bandpass Filter See Printed Manual Single BandpassFilter Results - See Printed Manual EXAMPL9 This circuit is an active delay line with a gain of 20dB and a 100uS constant within 3% to 3khz. Up till now the circuit Amplitude has been of paramount importance, but this is not always the case. The Time or Group delay has an important part to play especially in telecommunication circuits where poor Group delay response can introduce distortion. It is also possible to look at the open circuit input and output impedance. In this example select Config and then select Cartesian format. Do not change the referance impedance from the default of 100Mohms. In this example the circuit provides not only gain but almost constant Time-delay for frequencies up to 3khz. Analyse the circuit on a Linear sweep from 100hz to 3khz. 100uS delay Line See Printed Manual Delay Line Results - See Printed Manual EXAMPL10 This is quite a large circuit and demonstrates how ACIRAN can handle even the most complex analysis. LowPass Filter See Printed Manual Low Pass Filter Results - See Printed Manual The circuit is a five stage GIC Elliptic-function Low Pass filter. It is to have low insertion loss and ripple in the pass band up to 260Hz, and to have a minimum attenuation outside the passband of 60dB at 270Hz. In practice variable resistors are needed to adjust the GIC to obtain the desired response. Analyse the circuit from 100 to 300Hz in 10 Linear steps. This circuit will take several minutes to Analyse. Exampl11 This example uses a Transmission line as a quarter wavelength transformer to match an impedance of 95 ohms real to a load of 50 ohms real. The frequency of interest is 150Mhz (2m wavelength) which gives a line length of 50cm (2m/4). The impedace of the line to give the required match is equal to the square root of the source impedance multiplied by the load impedance ie. sqrt(95 * 50) = 69ohms Transmission Line Transformer See Printed Manual Where Zo = characteristic impedance L = length in cm Er = relative permeability The configure menu is entered and the load impedance set to 50 + j 0.00 and the generator impedance to 95 + j 0.00. Select Return loss and Linear Sweep. Analyse the circuit from 148Mhz to 152Mhz in 4 steps, the results are:- Transmission Results for Transmission Line Transformer - See Printed Manual Exampl12 This example makes use of transmission lines to match a source impedance to a complex load by means of a Stub Tuner. The theory of Stub Tuner matching is beyond the scope of this manual and the reader should refer to relevant text books. Stub Tuner See Printed Manual A Stub can be open or short circuit, it is better to use a short otherwise it tends to radiate. The circuit was analysed over the same frequency range as before. The source generator was set to 50 + j 0.00 ohms and the load set to 100 + j 50.00, ie complex. Transmission Results for Single Stub Match - See Printed Manual Where Zo = characteristic impedance L = length in cm Er = relative permeability At first appearance the passive line seems to have a gain, this is due to the impedance transformation, and although a voltage gain is produced the current gain is less than unity and so is the power gain. Appendix ACIRAN uses model files to hold descriptions of Transistors Fets and Opamps. You can create your own model files and add them to the Models directory using any text editor or wordprocessor such as WordStar (Do not use any control codes). Details can be found in the Printed Manual. The model for the BC107 transistor used in EXAMPL2 is BC107 2.7k 18U 192 35% 300M The file consists of lines of text. Each line contains ONE and only one parameter and all parameters MUST be supplied. The information can be obtained from manufacturers data sheets. The first line contains the component name 'BC107' ( max of 8 characters). Next comes the value of hie, followed by hoe and hfe. The tolerance value refers to hfe. Transistor hfe values can vary enormously even for the same type of transistor. The 'h' parameters of a transistor vary with temperature and collector current. Last comes the value of FT. Note the use of multipliers, hie could just have easily been written as 27e2, 27E2 or 2700. Transistor model files MUST be given the extension .TRN. The Fet model file for the 2N4393 Fet used in EXAMPL6 is shown below: 2N4393 15m 45% 11.5p 2p Again the same rules apply as for the transistor file. First comes the name, followed by the transconductance gm, the tolerance for gm, the Fet capacitances Cgs and Cgd. Fet model files MUST have the file extension .FET. The last model type supported by ACIRAN is the Opamp model. The model file for the LM124 opamp is listed below: LM124 100M 600 100 1M 50% First comes the component name followed by the input impedance and the output impedance. Next is the open loop gain in dB and the Gain Bandwidth Product GBW. The tolerance refers to the open loop gain. Most opamps have a very high open loop gain in excess of 100dB. Manufacures data sheets give conservative values for open loop gain and it is well controlled. Opamp model files MUST have the extension .AMP. The Hybrid Pi model for a Transistor is illustrated below: See Printed Manual The symbols have the following meaning: rbb = Base spreading resistance rbe = Input impedance rbc = Feedback Impedance (effect of Vce changes on Base modulation) rce = C-E Impedance Cc = Collector-junction barrier capacitance Ce = Overlap diode capacitance gm = Transistor Transconductance If the CE 'h' parameters are known at low frequencies at a given collector current Ic (see manufacturers data sheets) then the impedances can be calculated in the following order: |Ic| |Ic ma | gm = ---- = -------- VT 26 hfe rbc = --- gm rbb = hie - rbe rbe rbc = --- hre 1 1 rce = ------------- where gbc = --- hoe-(1+hfe)gbc rbc The capacitance Cc is the measured CB output capacitance with the input open (Ie = 0), and is usually specified by the manufacturers as Cob. Ce is experimentally determined from a measurement of FT, the frequency at which the CE short-circuit current gain drops to unity. gm Ce = ------- PI = 3.14159 2*PI*FT Typical values for a Hybrid PI model at room temperature and for Ic = 1.3mA are gm = 50mA/V rbb = 100 ohms rbe = 1k rbc = 4Mohm rce = 80Kohm Cc = 3pF Ce = 100pF END.