Modeling of narrow-base bipolar transistors including variable-base-charge and avalanche effects

A bipolar transistor model, compatible with circuit analysis programs, that can model base punchthrough and avalanche breakdown conditions, is presented. The model equations are derived for low to medium current densities and the analytical and experimental methods of obtaining the required parameters are described. Simulation results using the WATAND circuit simulator are compared to experimental measurements for two different bipolar transistors and are shown to agree very well in the normal and inverse modes of operation.