Physical modeling of high-current transients for bipolar transistor circuit simulation

Existing bipolar transistor models for circuit simulation are extended to properly account for the possible existence of a high-current-induced space-charge region in the epitaxial collector region. The new physical model thus correctly simulates ohmic and nonohmic quasi-saturation (base push-out), for both steady-state and transient operation. High-current transients are accounted for quasi-statically, using a charge-based formalism. The model is implemented in SPICE, and representative simulations and measurements are presented to demonstrate both model utility and necessity.