SPICE
Beginner
A computer program that simulates a circuit’s transistors in detail to predict exactly how its voltages and currents change over time.
Novice
A family of circuit simulators that solve the equations of a transistor-level netlist using device models from the process kit. It is accurate but far too slow to run on a whole chip, so it is used on small circuits such as single cells.
Expert
Transient analysis with compact device models (BSIM and similar) on the extracted netlist, including parasitic resistance and capacitance. Characterizers drive it in batches, one simulation (or a sweep) per arc, slew, load and corner; ngspice and Xyce are open-source options.
Explained in From devices to a cell library (Transistors).
See also: Cell characterization.