What is SPICE? - dcback/PSpice GitHub Wiki

SPICE (Simulation Program with Integrated Circuit Emphasis) is a well-known circuit simulator computer program which began with a mainframe program written at UC Berkeley by Lawrence Nagel (and others) during his PhD. The SPICE solver or “engine” (the core part of the program i.e.the part that solves the circuit equations) is free software but it is command line driven and is thus regarded as difficult to use. Consequently, several commercial versions (mostly based on the 2G7 release of the Berkeley program) are available which provide a graphical interface and up to date component libraries (models of commercially available semiconductor components provided by the semiconductor manufacturers).

PSpice is such a commercial implementation for MS Windows and is sold by OrCAD (http://www.orcad.com). It has a schematic GUI input and an oscilloscope-like output interface. The schematic input (called Capture) lets users draw circuits to be simulated on the screen and the oscilloscope-like output (called Probe) allows users to interactively plot traces after a simulation run. In between this input and output is what is basically the original SPICE solver (written by Nagel et al.) that reads the circuit definitions from “netlists” (a text file which describes the circuit by specifying components, their values and their interconnections) and runs the circuit simulation. In days gone by, users specified circuits by writing the netlist by hand in a text editor and the netlist file was effectively the input to the simulator. PSpice (and the other commercial SPICE implementations) create the netlist automatically from the circuit schematic drawn by the user (this process is called schematic capture).

An overview of the basic steps needed to run a simulation in PSpice is shown below (non-shaded bullet points are dealt with automatically by the PSpice program and most of the time the user does not need to concern themselves with these stages as (s)he would have done in the 1970s.):

  • Draw schematic of circuit
  • Set up Simulation
  • Run Simulation
    • Build netlist from schematic
    • Run SPICE solver on the netlist
    • Text files written as output
  • Plot output graphs