SPICE Source Types and Parameters


The National Instruments 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.




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




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



 Syntax  EXP(V1 V2 TD1 TAU1 TD2 TAU2)

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 <T2; V2 T3 V3 T4 V4 ...>)

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



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