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PSpice Tutorial

PSpice Tutorial. October 13, 2004. Franklin Chiang. Orcad Programs. PSpice Use “netlists” to code up circuits. Text based. Start  programs  Orcad Family Release 9.2  Orcad PSpice Capture Use diagrams to draw up circuits and simulate. Graphics based.

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PSpice Tutorial

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  1. PSpice Tutorial October 13, 2004 Franklin Chiang

  2. Orcad Programs • PSpice • Use “netlists” to code up circuits. Text based. • Start  programs  Orcad Family Release 9.2  Orcad PSpice • Capture • Use diagrams to draw up circuits and simulate. Graphics based. • Start  programs  Orcad Family Release 9.2 Lite Capture Lite

  3. Startup and Basic Syntax • Start  Programs  Orcad Release 9.2  PSpice • File  New  Text file • 5 different “commands” you can use • Title: first line of code (always) • .END: last line of code (always) • Comment: line denoted by * • Element: Resistor, capacitor, etc. • Control: analysis

  4. Passive Component Description • Resistor • R<name> <node1> <node2> <value> • Ex. R1 1 2 100 • Names should not contain comma, space, or =, or parenthesis • Capacitor • C<name> <node1> <node2> <value> • Ex CBYP 13 0 1uF • Inductor • L<name> <node1> <node2> <value>

  5. Units in PSpice • T = tera = 1012 • G = giga = 109 • Meg = mega = 106 • k = kilo 103 • m = milli = 10-3 • u = micro = 10-6 • n = nano = 10-9 • p = pico = 10-12 • f = femto = 10-15

  6. Source design • Independent Voltage Source • V<name> <+node> <-node> <dc/ac> <value> • VCC 10 0 DC 6 • Independent Current Source • I<name> <+node> <-node> <dc/ac> <value> • I_in 10 0 AC 3m

  7. Voltage Sources • DC: Vname n+ n- DC <value> • AC: Vname n+ n- AC <magnitude> <phase> • Transient: • Vname n+ n- sin(Vo Va freq td damp) • Vname n+ n- pulse(V1 V2 td tr tf PW T) • Vname n+ n- PWL(t1, v1, t2, v2, …, tn, vn)

  8. Active Devices (transistors!) • Usually given a model file as text file • Include it into pspice using: • .lib <name of file> • ex: .lib 115cmodel.txt • Make sure text file is in same directory

  9. Including your own model files • .model <name> <type> <parameters….> • .model QPNP PNP(Is=650.6E-18 Xti=3 Eg=1.11 Vaf=100 Bf=150 Ne=1.829 + Ise=54.81f Ikf=1.079 Xtb=1.5 Br=3.563 Nc=2 Isc=0 Ikr=0 Rc=.715 + Cjc=14.76p Mjc=.5383 Vjc=.75 Fc=.5 Cje=19.82p Mje=.3357 Vje=.75 + Tr=111.3n Tf=603.7p Itf=.65 Vtf=5 Xtf=1.7 Rb=10) • .model QNPN NPN(Is=14.34f Xti=3 Eg=1.11 Vaf=100 Bf=150 Ne=1.307 + Ise=14.34f Ikf=.2847 Xtb=1.5 Br=6.092 Nc=2 Isc=0 Ikr=0 Rc=1 + Cjc=7.306p Mjc=.3416 Vjc=.75 Fc=.5 Cje=22.01p Mje=.377 Vje=.75 + Tr=46.91n Tf=411.1p Itf=.6 Vtf=1.7 Xtf=3 Rb=10) • Copy, paste.

  10. Declaring transistors • BJT: • Q<name> <NC> <NB> <NE> <model> • Ex. Q23 10 24 13 npn • MOSFET: • M<name> <ND> <NG> <NS> <NB> <model> <various parameters> • M1 24 2 0 20 nmos • M2 2 9 3 0 pmos L=10u W=5u AD=100p AS=100p PD=40u PS=40u

  11. Building a circuit 1 2 • First, draw the diagram • Label nodes • Code in Pspice 3 3 4 0

  12. Code

  13. Analysis Types • DC Analysis • DC transfer curve source and sweep • .dc <source> <vstart> <vstop> <vincr> [src2 start2 stop2 incr2] • .DC VIN 0.25 5.0 0.25 • .DC VDS 0 10 .5 VGS 0 5 1 • “nested sweep”: for each VDS, sweep VGS from 0 to 5 incrementing by 1 each time. So total number of operations would be 20 * 5 = 100

  14. Analysis Types • Operating Point • .op • Calculates dc operating point of circuit with inductors shorted and capacitors open. • Useful in checking your work. • Results put in .txt file

  15. Analysis types • AC small signal • computes the ac output variables as a function of frequency • first computes the dc operating point of the circuit and determines linearized, small-signal models for all of the nonlinear devices in the • resultant linear circuit is then analyzed over a user-specified range of frequencies • Can be used to compute noise!

  16. Analysis Types • AC Analysis (cont) • .AC DEC ND FSTART FSTOP • Dec = decade variation, ND = pts. / decade • .AC LIN NP FSTART FSTOP • Lin = linear variation, NP = # pts • .NOISE OUTV INSRC NUMS • OUTV = output voltage which defines summing point • INSRC = name of independent source which is the noise input reference • NUMS = summary interval

  17. Analysis Types • Transient (.tran <step> <stop> <start>) • The transient analysis portion of SPICE computes the transient output variables as a function of time over a user specified time interval • The initial conditions are automatically determined by a dc analysis • Useful for 115C • .tran 1ns 1000ns 500ns

  18. Back to Resistor Bridge • Ex. Find voltage across R3 when Vin = 10V

  19. Results

  20. Transistor examples: IV curve • Plot I-V characteristic of NMOS with: • W = 1.2um • L = 0.25 um • Set Vdd = Vg = 2.5V, Vs = 0V D G ID S

  21. Solution: 3 • 1) Draw circuit with sources • 2) Label nodes! • 3) Code in spice 2 0

  22. Solution:

  23. Graph

  24. Inverter demonstration

  25. Results

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