Laboratory Experiment 1 EE348L
Contents
1. B Verify your results with HSPICE 1 Print out node voltages from the output file Compare them to the hand calculations Figure 1 11 Exercise 2 Figure 1 12 is aregular 741 op amp An op amp can be modeled in SPICE by using the equivalent circuitry found in Figure 1 13 A Compute the gain in figure 1 14 by hand Find the gain symbolically do not use resistor values Assume ideal op amp impedances but not ideal gain Rin oo A A Rout 0 1 If we want maximum voltage transfer to the input of the op amp should R1 gt gt Rs or should R1 lt lt Rs Why For the rest of the problem assume maximum voltage transfer 2 What is the limit of the gain as Ajo Let s call this the ideal gain or Ai 3 Using your results in part 2 modify your gain equation to be in terms of only Ai and Ao University of Southern California EE348L page26 Lab 1 4 What is the limit of the gain as A gt gt Ai How much larger than Ai should A be for the gain to be within 1 of Ai This exercise should give us an idea of either the lower limit of the gain of an op amp A for a particular ideal gain or the upper limit of the ideal gain for a particular op amp gain A B Given the circuit resistor values in figure 1 14 find 1 The ideal gain of the circuit Ai 2 The actual gain of the circuit if A ZAi 10Ai and 100A1 C Use the equivalent circuit figure 1 13 and HSPICE to verify your answers you found in part B Using a TRAN a2. Its drain is connected to node 3 while the gate source and bulk are connected to nodes 15 O ground O ground respectively SPICE sources the Model called typical for its physical characteristics The new addition of L and W describe the physical dimensions of the device L stands for the length of the channel while W stands for the width The type University of Southern California EE348L page16 Lab 1 of MOSFET is identified in the model statement In this example the MOSFET is a NMOS but replacing the NMOS part in the statement with PMOS will change the type of MOSFET from NMOS to PMOS A table of other typical MOSFET characteristics and their default values are listed in table 1 7 n 1 7 MOSFET model parameters Les MOSFET Model number Lesit kp Transeonductance coefficient uCax AN Xm a O O O Ra rain resistance Joms 0 Vo Threshold Voltage Vo amb a Channel Length Modulation v o amm Bodyefet V7 0 1 5 Command Statements Once you have entered all the element statements in the input file you have to enter the command statements These command statements tell SPICE exactly how you want to simulate the circuit and present the data As opposed to element statements all command statements begin with a period 1 5 1 Analysis type Once the element statements are complete the analysis that is to be done needs to be specified to S
3. To use a piecewise linear source state a voltage and the corresponding time you wish the source to reach that value In the example above at time 0 the source will have a value of OV The source will then perform a linear increase for the next 3ms till it reaches 5V The next point given has the same voltage value so the source will have the value of 5V for the next 3ms The source will then follow a linear degradation till it reaches 3V four milliseconds later Graphs of the time varying signals Amplitude sec Vo Va J g met Vo Time sec frequency Figure 1 2 4 SIN wave created in SPICE University of Southern California EE348L page9 Lab 1 V2 Amplitude volts time sec Amplitude volts 6 6 t1 v1 time sec H rem 1 4 A piecewise linear signal created in SPICE University of Southern California EE348L page10 Lab 1 1 4 2 Dependant Sources Dependent sources will be covered in more detail in the second lab They are introduced in this part If you have a voltage dependent source there are four nodes in the command If you have a current dependent source there are two nodes and a voltage source in the command The first two nodes of any dependent source n and n represent the node numbers for the positive and negative ports of the output NOTE current flows from the positive port to the negative port of sources If you have a voltage dependent source the second se
4. model statement called normal for all the physical characteristics normal indicates to Spice that the BJT called 1 is an NPN transistor and gives some associated characteristics The Model statement is easily modified to change the transistor to a PNP type Simply replace the NPN with PNP in the statement Table 1 6 give some basic characteristics variables for a typical BJT and the default values associated with each University of Southern California EE348L page15 Lab 1 Table 1 6 BJT model parameters BOO Sswaincurm O Amp 13105 Bf jForwadGain jUnitles 100 Rb Baseresistance Ohms Q 0 Ohms o Re Emitter resistance Ohms 0 Forward Early voltage Volts MOSFET Figure 1 8 Schematic symbol of MOSFETS G is the Gate terminal D is the Drain terminal S is the Source terminal B is the Bulk terminal The element statement structure for the MOSFET is basically the same as the BJT but with one more terminal An example is given and explained below Generic Mname D G S B Model name L value W value Later in the netlist a Model statement is required Model model name NMOS certain parameter 1l value certain parameter 2 value etc Example M55 3 1500 typical L lu W 20u Later in the Model statements Model typical NMOS kp 10u Vto 1 5 lambda 0 The MOSFET described by the example is called 55
5. 0 0 These elements fall into three different categories Signal Sources Passive Elements and Active Elements Voltage source Current source Vname Figure 1 1 Independent Sources 1 4 1 Independent Sources Three independent sources can be used in SPICE simulations A DC source a frequency sweeping AC source and time varying TRAN source can all be modeled with standard SPICE signal sources Each University of Southern California EE348L page6 Lab 1 source can either supply current or voltage Different types of sources are used for different types of analysis Table 1 2 lists the different element statements for independent sources and the analysis type that is typically used with each Table 1 2 Suuice element statements Vname n n AC mag phase SIN wave Voltage Vname n n SIN V V freq t damping Iname n n SIN V V freq Vname n n PULSE V V ta t ty PW T Iname n n PULSE V V ta t t PW T Vname n n PWL ti v t2 v2 Vn Iname n n PWL t v t2 v2 ts Vy Each element statement has an array of characters that represent different characteristics of the source The characters are separated by a space so that the compiler knows that the user is done describing one aspect and starting another In the element statements the first letter depicts if the source delivers voltage or current with a V or I respectively The first letter is followed by the name of that source Each source has to have a
6. 1m END Note SPICE is case insensitive A Schematic of the example input file Figure 1 9 Schematic of example input file The plots of nodes 1 and 2 as seen in WaveView Analyzer labi example1 06 15 2012 10 33 12 waveview 1 n 200u 400u 600u BOOY Im rn lt ttt doot te 11 11 Pott tt w 2 lab1 example1 tro 1 H v 1 lab1 exarmple1 tro 4 i H i o P S a a s a od E a a d a a a pee EIE Ae 4 pp o 200u 4cGu 60Cu BoOu am sec lin printad Fri Jun 15 2012 13 37 43 an aludra usc adu Synapsys Inc c 2000 2003 Figure 1 10 The output node 1 is in blue and the input node 2 is in red University of Southern California EE348L page22 Lab 1 This lab is no way intended to be a SPICE manual This introduction only covers the basics that a student will need to run SPICE Other published material such as the ones in the reference reading on SPICE should be consulted for a better understanding 1 8 Reference Reading 1 Gordon W Roberts and Adel S Sedra SPICE Second edition New York Oxford Press 1997 2 Marc E Herniter Schematic Capture with MicroSim Pspice Third edition Upper Saddle River New Jersey Prentice Hall 1998 3 HSPICE user manual http jcatsc com media ee348 Labs ee348_2001 4_hspice pdf 4 LTSPICE IV user manual http jcatsc com media ee348 CADandLabs LTspicelVRef pdf 5 PSPICE user manual http jcatsc com media ee348 CADandLabs
7. COMPARE YOUR RESULTS WITH YOUR PRE LAB INCLUDE YOUR PRE LAB RESULT IN YOUR LAB REPORT SIMPLY STATING THEY ARE THE SAME IS NOT GOOD ENOUGH NOTE You are turning in lab reports that are to be graded If you want good marks be sure to make the reports as neat and aesthetically appealing as possible If you refer to an attached plot include the page number If you refer to a hand calculation be sure to highlight what you are referring to on the page containing the hand calculation However including equations plots figures etc in the body of your report is good practice Be sure to include plot titles Be sure to include axis titles and units Lab reports are to be typed HANDWRITTEN REPORTS WILL NOT BE ACCEPTED LAB REPORTS ARE DUE AT THE BEGINNING OF THE NEXT LAB THEY WILL NOT BE ACCEPTED IF THEY ARE MORE THAN 15 MINUTES LATE University of Southern California EE348L page31 Lab 1
8. PSpiceRef pdf University of Southern California EE348L page23 Lab 1 1 9 1 9 1 1 2 3 1 9 2 1 2 3 4 1 9 3 1 2 3 4 HSPICE GUIDELINES REVIEW To Simulate a Circuit Write a netlist using a text editor such as emacs and save it as a sp file emacs sp Use the hspice command to simulate your circuit hspice circuit sp gt circuit out Read circuit out to see if there are any errors or warnings You must fix the errors while warnings may be ignored depending on severity This can be done with the more command more circuit out To plot the output of a circuit To plot the results of a simulation run WaveView Analyzer wv amp at the unix prompt Make sure you have used the opt post option or the probe command When WaveView Analyzer opens go to File Import Waveform File Select the output file s you want to view If you ran a TRAN you will open filename trO If you ran a DC you will open filename sw0 If you ran a AC you will open filename acO If you ran a OP or a TF the outputs can be viewed in the output file Select the data you wish to be plotted Some common wave view options printing To add a cursor go to Axes Cursor Add Cursor To change the background color to white go to Config Preferences Click on the Waveview tab For Waveview Background select White To export the wave view as a postscript go to File Print Near the bottom in the PostScri
9. after the 3db frequency Be sure to make the x axis logarithmic right click on the scale in WaveView Analyzer What should be the magnitude of the value of Vo at the 3db frequency Using the plot from part B add a curser at the 3db frequency Include all plots in your lab report University of Southern California EE348L page30 Lab 1 1 11 General Report Format Guidelines This guideline should be followed from a problem to problem basis for parts 2 5 For example start with 1 then for exercise 1 do parts 2 5 Then repeat for each other exercise Then wrap it up with parts 6 7 1 Introduction Explain what the lab is about Describe the circuits being built in terms of structure and purpose Also talk about what is being investigated For Each Exercise 2 Procedure Step by step talk about what was done and show diagrams of the circuits 3 Data Present data taken during the lab It should be organized and easy to read 4 Questions Answer all the questions in the lab 5 Discussion Discuss the results you obtained What significance is there in the results How do they help your investigation Explain the meaning the numbers alone aren t good enough 6 Conclusion Wrap up the report by giving some comments on the lab Do the results clearly agree with what the lab was trying to teach Did you have any problems Suggestions 7 Attachments Attach all hand calculations and SPICE plots necessary IF ALAB EXERCISE ASKS YOU TO
10. different name and they can be up to seven characters long Next the n and n denote the node number of the positive and negative terminal respectively You will assign numbers alphabetic characters are also valid in SPICE to all the nodes in your circuit when writing an element statement You may number or name them anyway you wish with the exception of ground SPICE interprets node Zero as the ground The type of signal is identified after the node numbers An example of each will be demonstrated DC Generic statement Vname n n DC value Example V110DC 10V This is a DC voltage source with a value of 10V named 1 and its connected with its positive terminal at node 1 and its negative terminal at node 0 ground The name is arbitrary you can call it anything you want AC Generic statement Vname n n AC mag phase Example University of Southern California EE348L page7 Lab 1 Vnew 5 0 AC 5V 2 This statement describes a frequency swept AC source called new that is connected to nodes 5 and 0 has a magnitude mag of 5V and contains phase shift of 2 degrees The phase can be left blank and SPICE will assume a zero degree phase shift SIN TRAN Generic statement Vname n n SIN Vo Va freq td damping Example Vinput 2 1 SIN OV 5V 10e3 5e 3 0 0 0 Vo is the initial voltage Va is the voltage amplitude freq is the frequency in Hz td is the time delay in seconds damping is the deca
11. 3 1 9 HSPICE GUIDBEINES REVIBW 2 ete rire tee eee e o eb ee ent et reta 24 1 9 1 To simulate a Carcuit ei CR ROC e ERE UR 24 1 9 2 To plot the output of a circuit eene ener enne nennen nnne 24 1 9 3 Some common wave view options eesseeseeeeeeeneneenneen nennen enne neen nennen enne erret 24 1 9 4 Some common user problems with SPICE cee ceseceseceseceseeeeeeeseeeaeeeaeceseeeseeeeeenaees 24 1 9 5 iDebugging o Solana vr RT UR SNR NR REPE E ERE IRR ONU Vrae 25 1 10 zLab xeteisesz eec ctr OH CR RE Eee rp Er A USES 26 1 11 General Report Format Guidelines eese nennen entrent 31 University of Southern California EE348L page2 Lab 1 Table of Figures Figure 1 1 An independent voltage and current SOUICE ee cece cece eee e eee e ee ee eee ee ene nm 6 Figure 1 2 A transient plot of a sine wave produced by a SIN source sss 9 Figure 1 3 A transient plot of a pulsed wave produced by a PULSE source ssssssss 10 Figure 1 4 A transient plot of a piecewise linear plot produced by a PWL source 10 Figure 1 5 A schematic representation of r c passive elements ssseeeee 13 Figure 1 6 A schematic representation of a diode sssssssee eene een 14 Figure 1 7 A schematic representation of a BUT cece ee ec eee eee e ee eee een ee et taeeeeeenaeeeeeetaeeeeennaa 15 Figure 1 8 A schematic rep
12. Laboratory Experiment 1 EE34SL Jonathan Roderick Onder Oz Tyler Rather Revised by Aaron Curry University of Southern California EE348L pagel Lab 1 Table of Contents 1 Experiment 1 SPICE Simulations l sscssssscssssscssscccssssscssssccssssscssssscssscsssecseees 4 1 1 Introduction 2h axe up oe ier les ae AR Ga Se p Hehe dds 4 1 2 First time HSPICE setup on your computer eeseeseeeeeeeeeer enne eene nennen entrent 4 T2 T To simulate a circuit e aed one CR AEE E RE EE EIE REM RE ERR 4 1 2 0 To view read simulation results of a circuit simulation sess 5 1 3 The NetliSt oot oer Er rente etr teh e etat e E iate te hisce 5 1 4 Circuit Blements Statements E RE e eere er e esten eet ee eo a ehe 6 I 4 1 Independent Sources iilii mirer Hetero ete ret DE Ce eie tesg 7 14 2 Dependant Sources 4e Sp eee dee ee re Gee ee 11 13 3 Passive Clements sic esent rete eer RUNS ste te elem TE IEEE ePi e e isse eS 13 4A Activecelements eite reet GEHE LR UTR LER HOME e Ur es CERE AEAN SN 14 1 5 Command Statement n stent te daa UR RR RP TES le ee es 17 15 1r Analysis type enge eee E E EE EEEE earl eta AR nee ER E EL 1 5 2 Outp t requested ee uen une tie nete E has petted eee dD 1 6 Graphical Interface Plots 3 ine dr t eite eiie Weta RAO Heo ERE RR eve 21 1 7 Example of an mput file 5 eI Sil uel Gadel ege AE aa ee 22 1 8 Reference Reading eie ne ptc eet a c Eee OE cet as 2
13. PICE This is done with an analysis request statement When creating an input file you must decide from the start what type of analysis you want to perform As listed in table 1 2 some independent sources only work with certain types of analysis There are four basic types of analysis to choose from DC operating point DC sweep AC frequency response and transient response TRAN An example of each analysis request statement is done below DC operating point requested OP The OP command is used when you want to know the DC operating point node voltages element currents power dissipation etc It gives the DC information of the circuit without sweeping anything DC sweep Generic statement DC source name starting value ending value step value A DC sweep is done for many reasons For example you would use a DC sweep if you wanted to see the different responses of a circuit for different biasing conditions Example DC power 0V 5V 0 1V University of Southern California EE348L page17 Lab 1 In the example the DC analysis command instructs the source named power in the circuit to start at OV and increase its values by increments of 0 1V until it reaches a value of 5V then it stops AC frequency response Generic AC type number of points frequency start frequency stop The AC command does not need the name of the source An AC source is the only source that allows for this type of analysis so HSPICE
14. Probe statement tells Spice to save information but not output it HSPICE usually saves all voltages and SUPPLY currents but to save information about variables the PROBE statement should be used The output gives information on what you are measuring you can measure voltage voltage difference or current through any element and the node number where you want to observe the activity of the circuit You many request data from multiple outputs just separate the output requests with a space Table 1 9 lists different output statements that may be used to measure voltage voltage difference or current in a circuit University of Southern California EE348L page19 Lab 1 Table 1 9 Data collection methods for print and plot commands Measuring Voltage at a specific node V node number Voltage difference between two nodes V node numberl node number2 Current through any element I Element name Some examples are done below Probe Generic Probe output Example Probe ac gain par 20 log10 v out v in Probe dc I Rout The first example will save the ac results of the gain of the transfer function v out v in in db The second example will save the dc current through the resistor out Print Generic PRINT type output Example PRINT DC V out This example will print the values of the node voltage called out from the DC sweep in a table in the output file Plot Generic Plot t
15. a OA initial condition 1 4 4 Active elements You will be using these elements in labs later in the semester They are introduced here The three basic active elements needed for this class are the diode BJT and the MOSFET The element statements for active devices are really similar to passive The fundamental difference is that the BJT and MOSFET are three and four terminal devices respectively The physical characteristics can also be a little more complicated Other than that active elements follow the same basic element statement format The first letter identifies the device type the next three statements are for the node numbers only two in the case of the diode and the last part of the statement contains the physical characteristics Since active devices have complicated physical characteristics a Model Statement is used An example of a diode BJT and MOSFET are all show below To better illustrate this technique they will have an accompanying explanation Diode Figure 1 6 A schematic symbol of a diode a represents the anode terminal represents the cathode terminal Generic Dname a c model name Later in the netlist a Model statement is required Model model name D certain parameter 1 value certain parameter 2 value etc Example Drec 2 3 fermi Later in the Model statements Model fermi D Is 150pA n 1 2 This example is of a diode named rec It is connected between nodes numbe
16. e and close the setup file Now in the command prompt source it source setup NOTE Each time you log on and open the hspice directory you will need to source the setup file to use the hspice wv and distill commands 6 You are now ready to run HSPI CE and use WaveView Analyzer 1 2 1 To simulate a circuit With SPICE you will need to first create a netlist A netlist is a text file that describes the circuit and analysis desired You then simulate the netlist and store the results in an output file After simulation you are able to view the results from the analysis requested by either viewing the output file or using WaveView Analyzer 1 Write a netlist using a text editor such as emacs and save it as a sp file emacs circuit sp University of Southern California EE348L page4 Lab 1 2 Use the hspice command to simulate your circuit hspice circuit sp If you want to save your output operating point in the file named circuit out then use the following command hspice circuit sp gt circuit out 3 Read circuit out to see if there are any errors or warnings You must fix the errors while warnings may be ignored depending on severity This can be done with the more command more circuit out 1 2 2 To view read simulation results of a circuit simulation 1 An op analysis will require you to read the output file circuit out to determine the results of this analysis 2 To view your simulation results use the opt post op
17. ent flows from node vMirrorP to node vMirrorM remember SPICE is case insensitive The controlling or reference current flows through vMirrorControl Its gain is 2 Scale Factors and Units In SPICE When dealing with units there are certain scale factor abbreviations that SPICE will recognize The acceptable abbreviations for HSPICE are listed in table 1 3 Table 1 3 Scaling abbreviations Spice Abbreviation Metric Prefix Multiplication factor gig mega 107 SU 107 Ooo K kl 107 105 O Y ee eee F SPICE does not require you to label the units however here are the acceptable unit abbreviations It is recommended to NOT specify the units since they can be confused for a scale factor see caution below Table 1 4 Unit abbreviations Degee y y Dee O Caution If not caught SPICE has a really fatal flaw If you notice the abbreviation for Farads and femto are both F This can be a cause for real heart burn If you were to label your capacitance value 1F thinking this represents one farad you would soon find out that spice interprets this as 1 femto farad 1e 15 Farads Again it is recommended to just not specify the units Another common mistake is mixing up mega with milli For example if you want to make a resistance of 1 mega ohms and use m instead of meg you will create a resistance of 1 milli ohms Universi
18. er wants to run a AC analysis but uses a SIN source which should be used for a TRAN analysis Specifying the wrong sweep values For example the 3 db value is 1kHz but the user sweeps from 10kHz 1GHz 10 The user forgets to include the ground node 0 in their netlist 1 9 5 1 2 3 4 5 Debugging Debugging problems with SPICE simulations is very similar to debugging computer programs It is important to follow an orderly procedure Make sure that there are no typographical errors See the section on common user problems in SPICE Make sure that the syntax of SPICE commands in the netlist is correct Make sure that the circuit represented in the netlist is what you want Make sure that the SPICE netlist the circuit sp file has the correct analysis statement with the correct parameters and the correct type of source for example a source with AC magnitude and optional phase for an AC analysis University of Southern California EE348L page25 Lab 1 1 10 Lab exercises A SPICE netlist for each problem should be attached to your lab report You may NOT work in groups for the first 2 labs You may collaborate but each student must turn in their own individual SPICE netlists Exercise 1 A Calculate by hand the volages at all the nodes and the current through resistors R3 R4 and R5 in figure 1 11 R1 2k R2 500 R3 2k R4 1 5k R5 1k R6 10k R7 2 2k R8 200 V1 3 3V V2z5V 1 Show hand calculations
19. ges then you don t need to include any PLOT or PRINT statements If you would like to plot element currents or variables then you will need to use the PROBE statement To open WaveView Analyzer after a simulation use the following command unixprompt wv amp The ampersand allows you to continue to use the unix machine and make changes to your sp file and re simulate while WaveView Analyzer remains open Be sure to reload the waveform in WaveView Analyzer if you do so Once you have WaveView Analyzer open you will need to add the simulation data to be plotted You will open three different file types depending on which type of analysis you ran If you ran a DC you will open circuit swO If you ran a AC you will open circuit acO If you ran a TRAN you will open circuit tr0 Once the file is loaded double click on the file name in the Output View sub window and then click on toplevel Below there will be listed all the available plots node voltages and if PROBE was used element currents and variables There is much to learn in WaveView Analyzer and the more one uses it the better one gets For printing see section 1 9 HSPICE Guidelines Review University of Southern California EE348L page21 Lab 1 1 7 Example of an input file Example input file This must be the first line of the file opt post Vs2 0 SIN OV 1V 10k R121 10k D1 1 0 diode MODEL diode D Is 2E 13 N 1 1 OP TRAN 01m
20. he circuit for 10ms and takes data points every 10ns Transfer Function Generic TF V node source University of Southern California EE348L page18 Lab 1 The TF analysis is useful for finding small signal gain and input output impedances This will make more sense later in the semester Example TF V out Vin TF V 2 1 Vin TF I Rout Vin These examples all compute the DC small signal transfer functions for different outputs with respect to Vin The first example finds the transfer function from the node called out to Vin The second example finds the transfer function from the differential voltage from nodes 2 to 1 to Vin The third example finds the transfer function from the current in the resistor called out to Vin 1 5 2 Output requested With SPICE you can request the data collected to be in the form of data points or as a plot This is done with a PRINT or PLOT statement The type of print or plot statement depends on what type of analysis you requested Table 1 8 lists these statements AC PRINT AC owtput O PoC TRAN PRINTTRAN output O pus MEM 0 AC PLOT AC output lower limit upper Timi TRAN PLOT TRAN output Gower limit upper limit AC PROBE AC ouput TRAN PROBETRANouwpu You will be able to view the data collected from the Print and Plot requests in the output file that is created once you simulate the input file through SPICE The
21. nalysis let Vs be a SIN source with amplitude of 50mV and a frequency of 500Hz Use the opt post option and WaveView Analyzer for your plots 1 What should tstep be if we want 1000 points period 2 What should tstop be if we want to plot 2 periods 3 Simulate for A Ai Plot Vo and Vs on the same panel and attach a curser to verify the gain calculated in part B 4 Repeat for A 10Ai and A 100Ai D It should be noted that as A gt the two input nodes approach the same value Repeat the simulation from part C but this time plot each input node of the op amp Note the changes when A goes from Ai to 100 A1 E Now do not let Rout 0 but let A 7 oo as we just saw this implies each input node to the op amp are at the same voltage Find the following gains in figure 1 14 by hand symbolically 1 Vo Vs Should this be any different from Vo Vs found in part A Why 2 Vz Vo 3 VZ Vs Is it necessary to go through KVL KCL for this if we have already found the previous two Why Hint A good way to check your work is to realize that Vz Vs Vo Vz Vo Vs 4 Is Vz Vs larger or smaller than Vo Vs By what factor 5 If Rout lt lt R2 Rf what is Vz Vo 6 If Rout R2 Rf what is Vz Vo 7 If Rout gt gt R2 Rf what is Vz Vo F Given the circuit resistor values in figure 1 14 find 1 R2 Rf Let s call this Rseen 2 The gains Vz Vo and Vz Vs if Rout Rseen 100 3 The gains Vz Vo and Vz Vs if Rout Rseen G Use
22. nia EE348L page5 Lab 1 1 4 Circuit Elements Statements Each element is described to spice in the input file by an element statement These statements contain the element name the nodes where the element is located and the physical characteristics of the element The first letter in the element statement identifies what type of element the statement is for The next two two terminal device three three terminal device four four terminal device etc characters of the statement are for the node numbers that the terminals are connected to The last part of the statement contains the physical model of the element If certain device physical characteristics are left blank then SPICE has a set of default values that it will automatically use Even though SPICE has some default values for a limited number of device characteristics some parameters cannot be left blank Table 1 1 contains a list of some basic elements and the letter that is used to identify them Table 1 1 Device Letter abbreviations First Letter 8 5 00 Element C Capacitor S D JDide 0 E J Voltage controlled voltage source VCVS Voltage controlled current source VCCS H JjCurrntcontrolled voltage source VCCS pti RR Independent current source Inductor 0 0 0 000000 00 00 M MOSET Q BIT J J J R Resistor 0 0
23. o of such versions are LTSPICE provided for free by Linear Technology and PSPICE provided for free by Cadence Design Systems Another very popular version is HSPICE which is distributed by Synopsis and whose license has been purchased by USC The most powerful version of these is HSPICE and thus this lab will provide all SPICE code in HSPICE However if a student wishes to use another version of SPICE they are free to do so For the most part SPICE code is universally accepted by SPICE engines However there are some differences in available commands and syntax from version to version Therefore if any problems are encountered by the version of SPICE you are using you need to look at its reference manual to make sure you are using it properly Links to the SPICE manuals for HSPICE LTSPICE and PSPICE are provided in the references section at the end of this lab and are also posted on the course website 1 2 First time HSPICE setup on your computer NOTE Textinthe courier font signifies Unix command line input 1 Log in to your campus Unix account using putty xwin or a vncserver vncviewer 2 Create a new directory to be used for HSPICE mkdir hspice 3 Create a setup file using a text editor such as emacs emacs setup 4 In the setup file add the following three lines source usr usc hspice 2010 03 SP 1 setup csh alias wv usr usc wave view analyzer c2009 03 sx c2009 03 bin wv alias distill usr usc acrobat 4 0 bin distill 5 Sav
24. pt Output File check the box marked Print To File In the Output Path text box name your file filename ps in the path you wish Click Print To convert from ps to pdf you will need to run the distill command distill filename ps This will create filename pdf NOTE Wave View has many tools and options The more you use and play with it the better you will get with it 1 9 4 1 2 3 4 5 Some common user problems with SPICE Typing op instead of typing op typing tran instead of tran etc Missing end at the end of the netlist Please make sure that you hit carriage return the enter key on the keyboard after the end statement Mistyping the netlist or using letters instead of digits Incorrect syntax for source statements in HSPICE Having floating nodes in the netlist To simulate an open use a very large resistor like 1 gigaohm where the open is University of Southern California EE348L page24 Lab 1 6 7 8 9 Incorrect number of arguments for control statements in SPICE An example of an incorrect SPICE control statement is the following which is missing one of the parameters of the PULSE statements see page 5 of this lab V1 12PULSEO 5 Im 1p 5m 10m Using the wrong units For example user types 1M to specify 1e6 which SPICE interprets as 1e 3 1 milli Using the wrong analysis type for the sources used For example the us
25. r 2 and 3 This diode references its physical characteristics from a Model statement called fermi In this particular example the only parameters dictated to Spice are Is and n More parameters can be specified if desired Table 1 5 is a list of typical parameters specified for a diode and the default setting for each University of Southern California EE348L page14 Lab 1 ues 1 5 Diode model parameters Spice Abbreviation Diode eC haracteristics Default ie saran cuentas Ix 16 Rs Ohmic Resistance n Ideality factor Unit less gu BV Revers biasbreakdownvollage Vols J Reverse bias breakdown current Amp Ix10 X BJT Figure 1 7 Schematic symbol for BJTs B is the Base terminal C is the Collector terminal E is the emitter terminal The BJT element statement is very similar to the diode The main difference is that it has three terminals instead of two Other than that the structure of the statement is very similar An example of a NPN is done below Generic Qname CBE model name Later in the netlist a Model statement is required Model model name NPN certain parameter value certain parameter 2 value etc Example Q13 14 5 normal Later in the Model statements Model normal NPN Is 3e 14 Bf 150 Vaf 30V The example statement describes a BJT with its collector connected at node 3 base connected at node 14 and emitter connected at node 5 It references the
26. resentation Of a MOSFET ssssssssseseeeenee nennen nnns 16 Figure 1 9 A schematic representation of the sample HSPICE input file ssssssssss 22 Figure 1 10 A transient plot of the input and output nodes from the sample HSPICE input file 22 Figure 1 11 A circuit schematic for lab exercise 1 ssssssseeee enm eene 26 Figure 1 123 A regular 741 pai sid deo iei tepaes tile ists aiu ete e ar atinira Eara a irainen 28 Figure 1 13 An equivalent circuit for Figure 1 12 to be used in HSPICE sssessssesesss 28 Figure 1 14 A circuit schematic for lab exercise 2 nennen 29 Figure 1 15 A circuit schematic for lab exercises 3 amp 4 sssssssssssseeeen eene 30 University of Southern California EE348L page3 Lab 1 1 Experiment 1 SPICE Simulations Part I 1 1 Introduction This experiment is designed to familiarize the student with SPICE SPICE simulations will be needed for prelabs and projects contained in this lab manual Spice is an acronym for Simulation Program with Integrated Circuit Emphasis SPICE is a computer aided design CAD tool that should be used to support design and should never be used in place of traditional design methods Design by SPICE is a trap that many circuit designers fall into and it causes a designer to lose the insight that makes one truly successful There are many different variations of SPICE that are produced by companies Tw
27. t of node numbers represents the positive and negative nodes of source s reference voltage If you have a current dependent source the current through the voltage source represents the controlling current An example of each will be demonstrated VCVS Generic statement Ename n n p p A lt MAX val gt lt MIN val gt Example Eone 2 3 1050 MAX 5 MIN 0 In the example the VCVS is named one Its output is connected between nodes 2 and 3 The controlling or reference voltage is between nodes 1 and 0 Its gain is 50 The maximum value is 5V and the minimum value is OV VCCS Generic statement Gname n n p p G lt MAX val gt lt MIN val gt Example Gm1 vout vs vin vs 50m In the example the VCCS is named m1 Its output current flows from node vout to node vs The controlling or reference voltage of the is between nodes vin and vs Its gain is 50 millisiemens CCVS Generic statement Hname n n vsource R lt MAX val gt lt MIN val gt Example H1 10 0 vcontrol 1k In the example the CCVS is named 1 Its output is connected between nodes 10 and 0 ground The controlling or reference current flows through vcontrol Its gain is 1kiloohms CCCS Generic statement Fname n n vcontrol A lt MAX val gt lt MIN val gt University of Southern California EE348L page11 Lab 1 Example Fmirror vMirrorP vMirrorM vMirrorControl 2 In the example the CCCS is named mirror Its output curr
28. the same HSPICE simulation stimulus as in part C with A 100 Ai However NOW WE WILL ADD RAILS Let the value of the rails be 9V See page 11 1 Simulate for Rout Rseen 100 Plot Vo Vz and Vs on the same panel Attach a curser to verify the gains Given the gains and input amplitude explain why clipping occurs if it does University of Southern California EE348L page27 Lab 1 2 Simulate for Rout Rseen Plot Vo Vz and Vs on the same panel Attach a curser to verify the gains Given the gains and input amplitude explain why clipping occurs if it does Hopefully now you see why we want Rout of an op amp to be much smaller than Rseen Remember to show all plots in your report W Vee Figure 1 12 Figure 1 13 University of Southern California EE348L page28 Lab 1 Figure 1 14 Exercise 3 A B C Use a transient TRAN simulation on the circuit in figure 1 15 to plot Vo with Vs Vs is a pulse generating source that alters between Ov and 5v The source should have a 1ms delay 5ms pulse width 10ms period and a rise and fall time of lps Using R1 2k and C1 1u plot Vo vs Vs for a tstep of lu and the following transient simulation times 1 30ms 2 300ms 3 3ms Do the results differ when using three different simulation times Why is it important to make an educated decision when choosing a simulation time for your simulation The time constant of a first order system refers to the
29. time it takes the system to reach within 1 e of its final value when the input is a step Vouz V fnat 1 6 What is the time constant of this circuit Verify this value with HSPICE by adding a curser to WaveView Analyzer and finding the time it takes for the output to reach 63 of its final value You may need to zoom in the x axis time to see this value Include all plots in your report University of Southern California EE348L page29 Lab 1 Figure 1 15 Exercise 4 A Using the schematic in figure 1 15 peform an AC analysis to plot a frequency sweep of Vo with B C 100 points per decade Replace Vs with an ac source with a magnitude of 1V Be sure to make the x axis logarithmic in your plots 1 Let Rl 1k and C1 100p Sweep from 10Hz 10kHz 2 Let R1 100k and C1 100n Sweep from 10Hz 10GHz 3 Why did both of these sweeps fail to show a valid AC sweep 4 Let R1 100 and Cl 1p Sweep from 10Hz 10GHz What is the problem with this sweep One can see that choosing the correct frequency range optimizes the results One common error ee348L students make is submitting poor plots An original sweep from DC to daylight can be a good way to get an idea of what frequency range is appropriate to sweep however this original plot should not be submitted Find the 3db frequency of the circuit in Figure 1 15 from part A number 1 remember 2 z f 442w 34 Run another ac sweep that sweeps two decades before and two decades
30. tion sometime use the probe command as well to save the data that can be viewed using WaveView Analyzer WaveView Analyzer can be opened using the wv command wv amp More on this later 1 3 The Netlist This is a model of a typical SPICE input file Title This must be the first line Description of the circuit s function Options Circuit Elements three kinds Sources Passive Circuit Elements Active Circuit Elements Model Statements Analysis Requested Output form Requested END Before saving the file make sure to press return once and only once after you type this statement The denotes a comment description or statement added by the writer of the spice code Any designated line with at the beginning will be skipped by the complier and will not have an effect on the actual code Any descriptions or comments can be omitted and the program will execute the exactly the same way Any comments descriptions or statements are for nothing more than the convenience of the reader The Circuit Elements category describes all the physical components that are contained in the circuit schematic Analysis Requested and Output form Requested are tools that are implemented in order to view a desired response from the circuit The end statement tells the compiler that the input file is finished Don t worry too much about capitalizing letters SPICE is case insensitive University of Southern Califor
31. ty of Southern California EE348L page12 Lab 1 1 4 3 Passive elements Passive element statements are very similar to DC sources The first letter indicates the passive element that is being used The letters for a standard resistor capacitor and inductor are listed in table 1 1 A schematic diagram of each is shown below The schematic diagrams accompanied by a generic statement an example statement and a brief explanation Figure 1 5 Schematic symbols of a resistor capacitor and inductor Resistor Generic Rname n n value Example R150 10k The example depicts a resistor named 1 which is connected between nodes 5 and 0 ground It has a value of 10k Ohms Capacitor Generic Cname n n value IC initial condition Example Cload 50 0 10u I C 0 5V This example is a capacitor named load connected at nodes 50 and 0 ground and it is 10 microfarads This capacitor also has a 0 5V initial condition This means that the capacitor has an initial voltage at time equal to zero If the IC initial condition part is left off SPICE will assume that the initial voltage on the capacitor is zero volts Inductor Generic Lname n n value IC initial condition Example Lfeedback 50 0 1 University of Southern California EE348L page13 Lab 1 This is an example of an inductor named feedback It is connected between nodes 50 and 0 ground and has a value of 1 Henry This particular inductor has
32. will implement this analysis to the AC source in the circuit automatically Following the AC command are statements that indicates the way points are taken and the number of points taken respectively Finally the starting and ending frequencies are listed There are three different types of AC frequency responses The difference deals with how the points are taken You can specify the following types DEC points are spaced logarithmically by decade OCT points are spaced logarithmically by octave or LIN points are linear spaced Example of the three different types AC DEC 100 2k 1e6 AC OCT 1000 2k 1e6 AC LIN 50 500 550 The first AC command depicts a statement that performs a frequency sweep that takes 100 points per decade The analysis starts at 2kHz and ends at IMHz The other two statements follow the same format Transient response Generic TRAN step time stop time The TRAN analysis is preformed when the response of the circuit with time is desired For example a transient response request would be used if you wanted to see the time it takes a capacitor to charge or discharge Caution For correct data collection make sure that the smallest step time in the transient command is equal to or smaller then the fastest change in your signal You must also make sure that the transient time complements the source or you will not be able to see the simulated results Example TRAN 10n 10m This example simulates t
33. y constant in 1 seconds This element statement describes a sinusoidal signal named input at it is connected between nodes 2 and 1 The signal has an initial voltage of OV and a magnitude of 5V It has a frequency of 10kHz and a time delay of 5milliseconds The signal has no damping factor If the statement does not contain values for td or damping then spice assumes a value of zero for both PULSE TRAN Generic statement Vname n n PULSE V1 V2 td tr tf PW T NOTE tr and tf are swapped when declaring a pulse in PSPICE Example V50 15 0 PULSE 2 5 0 2e 3 4e 5 5 10 0 VI is the lower voltage value V2 is the upper voltage value td is the time delay in seconds tr is the time in seconds it takes for the pulse to rise tf is the time in seconds it takes for the pulse to fall PW is the pulse width of the peak value or the time the pulse remains at the upper voltage value in seconds T is the time of one pulse period in seconds The example details a pulse named 50 It is connected to nodes 15 and 0 The pulse has a lower voltage value of 2V and an upper value of 5V The time delay is zero seconds while it takes 2ms and 40us for the pulse to rise and fall respectively The pulse spends 5 seconds at 5V and has a total period of 10 seconds University of Southern California EE348L page8 Lab 1 PWL TRAN Generic Vname n n PWL t1 v1 t2 v2 tn vn Example V100 25 10 PWL 0 0 3e 3 5V 6e 3 5V 10e 3 3V
34. ype output Example PLOT AC I R10 This example will plot the values of the current through the resistor called 10 from the ac sweep in the output file Special output requests Some special output requests can be made for AC simulations Just switch the identifying letter V or D in the output form listed above with a new abbreviation listed in table 1 10 University of Southern California EE348L page20 Lab 1 New Abbreviation VmImo y Vm Im Decibels Vdb Idb After you have entered all the elements analysis and output request you must end the input file with an END statement Make sure to press return after you have typed your END statement Not doing this sometimes hangs up SPICE 1 6 Graphical Interface Plots Again HSPICE plots are very crude and not the most presentable There are tools that you can use to plot the data once you have collected it You can use the PRINT statement then copy and paste the output data into excel or an equivalent and plot it that way There are also graphical interface programs designed to plot the data stored in you output file automatically One such program is WaveView Analyzer If you want to use WaveView Analyzer you must include the statement opt post right before your element statements This will save all node voltages by default but not element currents or variables If you are using WaveView Analyzer and you just want to plot node volta
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