# PSpice Textual Description

1.INTRODUCTION :

The SPICE is a software which works as a tool for electronic circuit simulation.In actually it is short form of SIMULATION PROGRAM WITH INTEGRATED CIRCUIT EMPHASIS.

• General purpose circuit program which can calculate and simulate the performance of electrical and electronic circuits.

• Perform various analysis of circuits: operating point analysis, time-domain response, a small signal frequency response

• A circuit is described by a file known as circuit file and must be specified in terms of element names, element values, nodes, variable parameters, sources, and the commands for what to calculate and what to provide as output.

• The circuit file is the input file to the SPICE program which produces the output file.

In short form we can defined it as- It is a general purpose analog electronic circuit simulator. It is a powerful program that is used in IC and board-level design to check the integrity of circuit designs and to predict circuit behavior.

2.VERSIONS OF SPICE TOOL :

• SPICE3

• HSPICE

• PSPICE

• AIM-SPICE

3.PSPICE VERSION :

PSPICE : This popular version of SPICE, available from Orcad (now Cadence) runs under the PC platforms. An evaluation (student) version, which can handle small circuits with up to 10 transistors, is freely available. For a full fledged version or for more information, please contact Orcad.

4.PROCEDURAL STEPS FOR PSPICE TOOL :

-Description of the circuit to SPICE

-Type of analysis to be performed

-Define the required output variables

5.FEATURES AND STRUCTURE :

TYPES OF ANALYSIS :

* Non-linear DC analysis (.DC)

* Non-linear Transient analysis (.TRAN)

* Linear AC analysis (.AC)

* Noise analysis (.NOISE)

* Sensitivity analysis (.SENS)

* Bias Point (.OP)

* Fourier analysis (.FOUR)

* Small Signal DC Transfer function (.TF)

* Others

.DC(DC ANALYSIS) :

Purpose : The .DC command performs a linear, logarithmic, or nested DC sweep analysis on the circuit. The DC sweep analysis calculates the circuit’s bias point over a range of values for<sweep variable name>.

General form .DC [LIN] <sweep variable name>+ <start value> <end value> <increment value>

+ [nested sweep specification]

.TRAN(TRANSIENT ANALYSIS) :

Purpose : The .TRAN command causes a transient analysis to be performed on the circuit and specifies the time period for the analysis.

General form : .TRAN[/OP] <print step value> <final time value>+[no-print value [step ceiling value]

.AC(AC ANALYSIS) :

Purpose : The .AC command calculates the frequency response of a circuit over a range of frequencies.

General form .AC <sweep type> <points value>+ <start frequency value> <end frequency value>

NOTE : <sweep type>-Must be LIN, OCT, or DEC.

<points value>-Specifies the number of points in the sweep, using an integer.

.OP(BIAS POINTS) :

Purpose : The .OP command causes detailed information about the bias point to be printed.

General form: .OP

NOTE : Using a .OP command can cause the small-signal (linearized) parameters of all the nonlinear controlled sources and all the semiconductor devices to be printed in the output file.

.TF(TRANSFER ANALYSIS) :

Purpose : The .TF command/statement causes the small-signal DC gain to be calculated by linearizing the circuit around the bias point.

General form: .TF <output variable> <input source name>

6.DEVICE MODELS :

* Analog device models

* Digital device models

*ANALOG DEVICES *

LetterDevice Type
BGaAsFET
CCapacitor
DDiode
EVoltage-controlled voltage source
FCurrent-controlled current source
GVoltage-controlled current source
HCurrent-controlled voltage source
IIndependent current source & stimulus
JJunction FET
KInductor coupling (and magnetic core)
KTransmission line coupling
LInductor
MMOSFET
NDigital input (N device)
ODigital output (O device)
QBipolar transistor
RResistor
SVoltage-controlled switch
TTransmission line
UDigital primitive summary
U STIMStimulus devices
VIndependent voltage source & stimulus
WCurrent-controlled switch
XSubcircuit instantiation
ZIGBT

*DIGITAL DEVICES*

Behavioral primitives
Bidirectional transfer gates
Delay line
Digital input (N device)
Digital output (O device)
File stimulus
Flip-flops and latches
Input/output model
Multi-bit A/D and D/A converter
Programmable logic array
Pullup and pulldown
Standard gates
Stimulus generator
Tristate gates

7.INPUTS AND OUTPUT FORMAT :
* Basically, SPICE operates like this:

1. Describe a circuit in a text file (“.cir” extension) called a netlist OR draw the circuit using graphical symbols on a schematic page.

2. Run a simulation. SPICE reads the net list and then performs the requested analysis: AC, DC, or TRANSIENT RESPONSE. The results are stored in a text output file (“.out” extension) or a binary data file.

3. View the results of the simulation in a text output file ( “.out” ) using a text editor. Most SPICE programs provide a graphical viewer to plot the waveforms stored in the binary data file.

INPUT CONTROL:

* MODELS : In this section we describe the models for elements using in the circuit. We have described type of models earlier.

* ANALYSIS : In this part give the type of analysis, what you want to find?

We have described type of analysis earlier.

OUTPUTS CONTROL:

• .PLOT (plot)- The .PLOT command causes results from DC, AC, noise, and transient analyses to be line printer plots in the output file.

General form :.PLOT <analysis type> [output variable]+( [<lower limit value> , <upper limit value>] )

• .PRINT (print)- The .PRINT command allows results from DC, AC, noise, and transient analyses to be an output in the form of tables, referred to as print tables in the output file.

General form : .PRINT[/DGTLCHG] <analysis type> [output variable]

• .PROBE (probe)- The .PROBE command writes the results from DC, AC, and transient analyses to a data file used by Probe.

General form : .PROBE[/CSDF][output variable]

• .END (end of the circuit)-The .END command marks the end of the circuit. All the data and every other command must come before it. When the .END command is reached, PSpice does all the specified analyses on the circuit.

8.POINTS TO BE REMEMBER BEFORE STARTING PSPICE :
• PSpice is not case sensitive

• All element names must be unique

• There must be a node designated “0” (Zero). This is the reference node against which all voltages are calculated.

• If any change is made in circuit make sure you create netlist again before simulating it.

• After completing the circuit save it and run it.

• Plot appropriate waveform by probing on circuit.

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