Download CS Alumni Advisory Board Presentation

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.
– Start  programs  Orcad Family Release 9.2
Lite Capture Lite
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
• 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
•
•
•
•
•
•
•
•
•
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
• 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
• 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!)
• 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
• .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
• 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
R1
1k
1
• First, draw the
diagram
• Label nodes
10V dc
• Code in Pspice
2
R2
R3
3k
5k
V1
3
3
R4
R5
3k
4k
R6
0
2k
4
Code
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 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 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 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 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
• Ex. Find voltage across R3 when Vin = 10V
Results
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 M1
ID
S
Solution:
3
• 1) Draw circuit with
sources
• 2) Label nodes!
• 3) Code in spice
V2
2.5
2
M1
V3
2.5
0
Solution:
Graph
Inverter demonstration
Results