PSpice Tutorial

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PSpice Tutorial

• October 13, 2004

Franklin Chiang
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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

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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

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Passive Component Description

• Resistor
• Rltnamegt ltnode1gt ltnode2gt ltvaluegt
• Ex. R1 1 2 100
• Names should not contain comma, space, or , or
  parenthesis
• Capacitor
• Cltnamegt ltnode1gt ltnode2gt ltvaluegt
• Ex CBYP 13 0 1uF
• Inductor
• Lltnamegt ltnode1gt ltnode2gt ltvaluegt

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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

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Source design

• Independent Voltage Source
• Vltnamegt ltnodegt lt-nodegt ltdc/acgt ltvaluegt
• VCC 10 0 DC 6
• Independent Current Source
• Iltnamegt ltnodegt lt-nodegt ltdc/acgt ltvaluegt
• I_in 10 0 AC 3m

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Voltage Sources

• DC Vname n n- DC ltvaluegt
• AC Vname n n- AC ltmagnitudegt ltphasegt
• 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)

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Active Devices (transistors!)

• Usually given a model file as text file
• Include it into pspice using
• .lib ltname of filegt
• ex .lib 115cmodel.txt
• Make sure text file is in same directory

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Including your own model files

• .model ltnamegt lttypegt ltparameters.gt
• .model QPNP PNP(Is650.6E-18 Xti3 Eg1.11
  Vaf100 Bf150 Ne1.829 Ise54.81f Ikf1.079
  Xtb1.5 Br3.563 Nc2 Isc0 Ikr0 Rc.715
  Cjc14.76p Mjc.5383 Vjc.75 Fc.5 Cje19.82p
  Mje.3357 Vje.75 Tr111.3n Tf603.7p Itf.65
  Vtf5 Xtf1.7 Rb10)
• .model QNPN NPN(Is14.34f Xti3 Eg1.11 Vaf100
  Bf150 Ne1.307 Ise14.34f Ikf.2847 Xtb1.5
  Br6.092 Nc2 Isc0 Ikr0 Rc1 Cjc7.306p
  Mjc.3416 Vjc.75 Fc.5 Cje22.01p Mje.377
  Vje.75 Tr46.91n Tf411.1p Itf.6 Vtf1.7
  Xtf3 Rb10)
• Copy, paste.

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Declaring transistors

• BJT
• Qltnamegt ltNCgt ltNBgt ltNEgt ltmodelgt
• Ex. Q23 10 24 13 npn
• MOSFET
• Mltnamegt ltNDgt ltNGgt ltNSgt ltNBgt ltmodelgt ltvarious
  parametersgt
• M1 24 2 0 20 nmos
• M2 2 9 3 0 pmos L10u W5u AD100p AS100p PD40u
  PS40u

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Building a circuit
1
2

• First, draw the diagram
• Label nodes
• Code in Pspice

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Code
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Analysis Types

• DC Analysis
• DC transfer curve source and sweep
• .dc ltsourcegt ltvstartgt ltvstopgt ltvincrgt 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

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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

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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!

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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

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Analysis Types

• Transient (.tran ltstepgt ltstopgt ltstartgt)
• 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

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Back to Resistor Bridge

• Ex. Find voltage across R3 when Vin 10V

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Results
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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
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Solution
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• 1) Draw circuit with sources
• 2) Label nodes!
• 3) Code in spice

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Solution
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Graph
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Inverter demonstration
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Results