Pspice Final

PSPICE

Introduction •

What’s Spice?

–

SPICE  Simulation Program with Integrated Circuit Emphasis

–

SPICE contains models for common circuit elements, active as well as passive.

•

Why Spice?

–

SPICE can provide information about circuit performance that is almost impossible to obtain with laboratory prototype measurements.

ORCAD PSPICE Using PSPICE the user can do three types of processes Capture Layout PSPICE A/D

Types of files in PSPICE A/D File Type

Description

.cir

The basic input file for PSPICE

.out

The output file generated. Contains Output data and errors

.dat

If too much data is produced (e.g. transient analysis) then this can be made as the output file and handled by the “probe”

.inc

include files, to store frequently used subcircuits not added to the library

.lib

library files

Specifying a Circuit File 

It has three main parts Element Statements : Describe the elements in the circuit ▫ Control Statements : Describe the types of analyses to be performed ▫ Output Statements : Specifies the output to be printed or plotted ▫

The circuit is described as elements connected between nodes.

General Structure of a Circuit File ;Title Statement Signal Source(s) Element Statements Control Statements Output Statements .end

Circuit File     



Comments must begin with * or ; First line is always a comment . The statements can be arranged in any order. The last line is always .end To continue a statement on a new line use the ‘+’ sign Each node must be uniquely labeled.

Elements 

PSPICE allows modeling of circuits with both active and passive elements like o o o o o

Resistor Inductor Capacitor Diode Transistor

PSPICE Elements

Prefix for units Code

Metric Prefix

Decimal Representation

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

1012

F

femto

10-15

Data Statements - Sources Independent DC Sources Voltage Source : Vname n+ n- Type Value Current Source : Iname n+ n- Type Value Type: AC or DC E.g. Vin 1 0 dc 12 Is 3 4 dc 1.5

Example

V1 V2

1 4

0 0

DC DC

10V 34V

Passive Elements 

SPICE considers the current always flows from the positive node through the element to the negative node. ELEMENT

PSPICE DESCRIPTION

Rname n+ nvalue Lname n+ n value Cname n+ nvalue

Example

Dependent Sources - VCVS Voltage Controlled Voltage source  Statement: Ename n+ n- nc+ nc- α 

Example *Name

n+ n- nc+ nc- gain Ebar 17 8 42 18 24.0;



First letter always ‘E’

Dependent Sources - VCCS Voltage Controlled Current Source  Statement: Gname n+ n- nc+ nc- γ 

Example:

*Name n+ Glab 23 

n17

NC+ 8

First letter always ‘G’

NC 3

γ 2.5

Dependent Sources - CCCS  

Current Controlled Current Source Statement: Fname Vmonitor



nn1

n+ n2

First letter always ‘F’

VMonitor DC 0V

β n1

n2

Dependent Sources - CCCS Example: *Name

Ftrn Vclt

n81 23

n+ 19 12

Vmonitor Vctl DC

Gain 50.0 0V ;controls Ftrn n1

n2

Dependent Sources - CCVS  

Current Controlled Voltage Source Statement: Hname n+ n- VMonitor gain Vmonitor n1 n2 DC 0V



First letter always ‘H’

Note  

 



PSPICE does not support open circuits . Every node must be uniquely labeled and must have at least two connections . Node 0 is always reserved for ground . In case analysis must be done on an open circuit, a very high resistance value must be used in place of an infinite resistance. PSPICE is not case sensitive.

Basic Analysis Types 

DC Analysis  



Transient Analysis 



.DC .OP .TRAN

AC Analysis 

.AC

Standard Analyses Commands       

.OP .DC .AC .TRAN .FOUR .NOISE .SENS

DC Analysis 

.OP Statement Causes detailed information about the bias point to be printed    



Voltage at the nodes Current in each voltage source Total power dissipation Operating point for each element

If not specified, it automatically performs a DC analysis before doing a transient or ac analysis

Example

ex 1.1.cir

V1 1 V2 4 R1 1 R2 2 R3 3 .OP .END

0 0 2 3 4

DC 10V DC 34V 6ohm 4ohm 2ohm

DC Analysis .DC Statement  Performs a linear, logarithmic, or nested DC sweep analysis  Calculates the circuit’s bias point over a range of values for <sweep variable name>

.DC Statement – Linear Sweep 

General Form

.DC [LIN] <sweep variable name> +<start value> <end value> +[nested sweep specification]

.DC Statement - LIST General Form .DC <sweep variable name> [LIST] * +[nested sweep specification]  Example 

.DC V1 LIST 2 4 8 9 13

Output Control Commands     

.PRINT .PLOT .PROBE .WATCH .VECTOR (for digital simulation)

.PRINT 



Allows results from DC, AC, noise, and transient analyses to be an output to the output file. (print tables) General Form

.PRINT

*

Example .PRINT DC V(1,2) I(R4) 

Example

ex 1.2.cir

V1 1 0 DC 10V V2 4 0 DC 34V R1 1 2 6ohm R2 2 3 4ohm R3 3 4 2ohm .DC V1 LIST -34V +0V 34V .PRINT DC V(1,4) +I(R1) .OP .END

.PLOT 



Causes results from DC, AC, noise, and transient analyses to be line printer plots in the output file. General Form

.PLOT [output variable]* + ([,])*

Example: .PLOT TRAN V(2) 

Example

ex 1.3.cir

V1 1 0 DC 10V V2 4 0 DC 34V R1 1 2 6ohm R2 2 3 4ohm R3 3 4 2ohm .DC LIN V1 0V 34V 1V .PLOT DC V(1,4) .OP .END

.PROBE 



Writes the results from DC, AC, and transient analyses to a data file used by Probe General Form

.PROBE [output variable]*  Example .PROBE V(2)I(R5)

Example

ex 1.4.cir

V1 1 0 DC 10V V2 4 0 DC 34V R1 1 2 6ohm R2 2 3 4ohm R3 3 4 2ohm .DC LIN V1 0V 34V 1V .PROBE .OP .END

Circuit File Processing Commands .END Marks the end of the circuit. 

Can there be more than one .END commands in a .cir file?

Find the currents in each branch using PSPICE R2 2 ohm

i1 ->

R1 2 ohm

2

3

i 2 _> Is1 12A

R4 _ 3 ohm i 5 > R3 1 ohm

1

_ i6 >

kcl.cir

R5 R6 3 ohm 6 ohm

i3 |v 0

i4 ^|

Is1 1 2 12A R1 2 3 2 R2 2 3 2 R3 1 0 1 R4 1 0 3 R5 3 0 3 R6 0 3 6 .DC Is1 LIST 12A .PRINT DC I(R1) +I(R2) I(R3)I(R4) +I(R5) I(R6) .OP .END

Find the voltages at nodes 1,2 ,3 R1 2 ohm

1 + -

Vs1 3V

R3 1 ohm

2 R2 6 ohm

1/4 v2

0 nodal.cir

3 R4 8 ohm

Vs1 1 0 3V R1 1 2 2ohm R2 2 0 6ohm R3 2 3 1ohm G1 3 0 2 0 0.25 R4 3 0 8ohm .DC Vs1 LIST 3V .PRINT DC V(1) +V(2) V(3) .OP .END

Find Thevenin Equivalent of the circuit to the left of points a and b R3 6 ohm Is2 15A

R5 1 ohm

1 + -

R1 2 ohm

2

3

a

Is1 15A

Vs2 20V

0

R2 3 ohm

b

Determination of Open Circuit Voltage R3 6 ohm Is2 15A

R5 1 ohm

1 + -

R1 2 ohm

2

Is1 15A

Vs2 20V

0

thevenin.cir

3

Vs2 1 0 20V R5 1 2 1 R1 2 3 2 R3 1 3 6 Is1 2 0 15A Is2 2 3 15A .DC Vs2 LIST 20V .PRINT DC V(3) .OP .END

Determination of output Resistance R3 6 ohm

1

R5 1 ohm

R1 2 ohm

2

3 + -

0

thevenin.cir

Vs1 5V

Vs2 1 0 0V R5 1 2 1 R1 2 3 2 R3 1 3 6 VS1 3 0 5V .DC Vs1 LIST 5V .PRINT DC V(3) +I(VS1) .OP .END

Find the Norton Equivalent of the circuit to the left of the points a and b R1 2 ohm

1

2

R2 1 ohm

3

a

+ + -

Vs1 3V

v1

R3 6 ohm

R4 1/4 V1 8 ohm

0

+ v -

b

a

1

+ R6 8 ohm 1.82 ohm

Is1 0.675A

R5

0

b

v -

Determination of short circuit current R1 2 ohm

1

R2 1 ohm

2

3

+ + -

Vs1 3V

v1

R3 6 ohm

isc | v

1/4 V1

0 R1 2 ohm

1

R2 1 ohm

2 +

+ -

Vs1 3V

v1

R3 6 ohm

0 norton.cir

3 Vs2 0V + i s c 1/4 V1

-

|v

Vs1 1 0 3V R1 1 2 2 R2 2 3 1 R3 2 0 6 Vs2 3 0 0V G1 3 0 2 0 0.25 .DC Vs1 LIST 3V .PRINT DC I(Vs2) .OP .END

Determination of output Resistance R1 2 ohm

R2 1 ohm

2

3

+ v1

R3 6 ohm

0

norton.cir

+ 1/4 V1

-

Vs2 5V

Vs1 1 0 0V R1 1 2 2 R2 2 3 1 R3 2 0 6 Vs2 3 0 5V G1 3 0 2 0 0.25 .DC Vs2 LIST 5V .PRINT DC I(Vs2) +V(3) .OP .END

.PARAM  



Defines the value of a parameter. A parameter name can be used in place of most numeric values in the circuit description. Parameters can be constants, or expressions involving constants, or a combination of these, and they can include other parameters.

Examples .PARAM VSUPPLY = 5V .PARAM VCC = 12V, VEE = -12V .PARAM BANDWIDTH = {100kHz/3}

.STEP The .STEP command performs a parametric sweep for all of the analyses of the circuit. General form 

.STEP LIN <sweep variable name> <start value> +<end value>

Examples .STEP VCE 0V 10V .5V .STEP LIN I2 5mA -2mA 0.1mA .STEP LIN PARAM Res .5k 10k .5k

Example – Plot the variation in power absorbed by load R2 as it varies between 500Ω and 10kΩ. When is it the maximum ? VS1 1 0 DC 5V R1 1 2 5k R2 2 0 {Res} .PARAM Res 4K .STEP LIN PARAM Res .5k 10k .5k .DC VS1 LIST 5V .PROBE .OP .END

param.cir

Source: http://www.tdpcb.com/images/pcb6.JPG