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SPICE is a general-purpose circuit simulation program for nonlinear dc, nonlinear transient, and linear ac analyses. Circuits may contain resistors, capacitors, inductors, mutual induc- tors, independent voltage and current sources, four types of dependent sources, transmission lines, and the four most common semiconductor devices: diodes, BJT's, JFET's, and MOSFET's.
SPICE has built-in models for the semiconductor devices, and the user need specify only the pertinent model parameter values. The model for the BJT is based on the integral charge model of Gummel and Poon; however, if the Gummel- Poon parameters are not specified, the model reduces to the simpler Ebers-Moll model. In either case, charge storage effects, ohmic resistances, and a current-dependent output conductance may be included. The diode model can be used for either junction diodes or Schottky barrier diodes. The JFET model is based on the FET model of Shichman and Hodges. Three MOSFET models are implemented; MOS1 is described by a square-law I-V characteristic MOS2 is an analytical model while MOS3 is a semi-empirical model. Both MOS2 and MOS3 include second-order effects such as channel length modulation, subthres- hold conduction, scattering limited velocity saturation, small- size effects and charge-controlled capacitances.