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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

PSpice Tutorial

October 13, 2004

Franklin Chiang


Orcad programs
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


Startup and basic syntax
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


Passive component description
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>


Units in pspice
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


Source design
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


Voltage sources
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)


Active devices transistors
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


Including your own model files
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.


Declaring transistors
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


Building a circuit
Building a circuit

1

2

  • First, draw the diagram

  • Label nodes

  • Code in Pspice

3

3

4

0



Analysis types
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


Analysis types1
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


Analysis types2
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!


Analysis types3
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


Analysis types4
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


Back to resistor bridge
Back to Resistor Bridge

  • Ex. Find voltage across R3 when Vin = 10V



Transistor examples iv curve
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


Solution
Solution:

3

  • 1) Draw circuit with sources

  • 2) Label nodes!

  • 3) Code in spice

2

0






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