# SPICE Source Types and Parameters

## Overview

The NI SPICE Simulation Fundamentals series is your free resource on the internet for learning about circuit simulation. The series is a set of tutorials and information on SPICE simulation, OrCAD pSPICE compatibility, SPICE modeling, and other concepts in circuit simulation.

For more information, see the SPICE Simulation Fundamentals main page.

The series is divided among a number of in-depth detailed articles that will give you HOWTO information on the important concepts and details of SPICE simulation.

Circuit simulation is an important part of any design process. By simulating your circuits, you can detect errors early in the process, and avoid costly and time consuming prototype reworking. You can also easily swap components to evaluate designs with varying bills of materials (BOMs).

#### SPICE Simulation Sources

SPICE allows users to specify input that varies in form. These inputs are used as voltage or current signals that drive circuitry during simulation. In Multisim, these sources are available in the Sources group of the master database.

The following sources are available in SPICE simulation.

## Using SPICE Simulation Sources

The table below gives detailed information on the usage of each SPICE source.

#### Pulse

 Syntax PULSE(V1 V2 TD TR TF PW PER) Example VIN 3 0 PULSE(-1 1 2NS 2NS 2NS 50NS 100NS)

 Parameter Description Default Units V1 Initial value Volts or Amps V2 Pulsed value Volts or Amps TD Delay time 0.0 Seconds TR Rise time Tstep Seconds TF Fall time Tstep Seconds PW Pulse width Tstop Seconds PER Period Tstop Seconds

#### Sinusoid

 Syntax SIN(VO VA FREQ TD THETA) Example VIN 3 0 SIN(0 1 100MEG 1NS 1E10)IN 3 0 PULSE(-1 1 2NS 2NS 2NS 50NS 100NS)

 Parameter Description Default Units V0 Offset Volts or Amps VA Amplitude Volts or Amps FREQ Frequency 1/Tstop Hz TD Delay 0.0 Seconds THETA Damping Factor 0.0 1/Seconds

#### Exponential

 Syntax EXP(V1 V2 TD1 TAU1 TD2 TAU2) Example VIN 3 0 EXP(-4 -1 2NS 30NS 60NS 40NS)

 Parameter Description Default Units V1 Initial value Volts or Amps V2 Pulsed value Volts or Amps TD1 Rise delay time 0.0 Seconds TAU1 Rise time constant Tstep Seconds TD2 Fall delay time TD1 + Tstep Seconds TAU2 Fall time Tstep Seconds

#### Piece-Wise Linear

 Syntax PWL(T1 V1 ) Example VCLOCK 7 5 PWL(0 -7 10NS -7 11NS -3 17NS -3 18NS -7 50NS -7)

 Parameter Description Default Units V1 Instantaneous voltage Volts or Amps T1 Instantaneous time Seconds

#### Single Frequency FM

 Syntax SFFM(VO VA FC MDI FS) Example V1 12 0 SFFM(0 1M 20K 5 1K)IN 3 0

 Parameter Description Default Units V0 Offset Volts or Amps VA Amplitude Volts or Amps FC Carier frequency 1/Tstop Hz MDI Modulation index Seconds FS Signal frequency 1/Tstop Hz