Compact model
Beginner
A set of formulas that lets a computer predict how a transistor will behave, so engineers can test circuits before building them.
Novice
A set of equations with fitted parameters that a circuit simulator such as SPICE uses to compute a transistor’s currents and charges from its terminal voltages. The foundry fits the parameters to measured devices and ships them in the process design kit.
Expert
Physics-based, all-region equations (BSIM4 for planar bulk, BSIM-CMG for FinFETs and multi-gate devices, PSP and others) with hundreds of parameters, fitted per process and corner. Continuity of currents and their derivatives across regions is essential for the simulator’s Newton iterations.
Explained in The I-V curve (Transistors).
See also: PDK (process design kit), Square-law (Shockley) model.