Implementation of Delay-Time-Based Nonquasi-Static Bipolar Transistor Models in Circuit Simulators

We found that for a correct simulation of nonquasi-static (NQS) effect in compact bipolar transistor models, a dynamic or small-signal transit time must be used instead of the classical dc transit time. It is shown that the dynamic transit time is slowed down compared with the dc transit time of the intrinsic device owing to the bias-dependence of the latter. Since the instance value of the dynamic transit time is needed at the operating point, a formerly proposed scaling technique is used. The model shows perfect agreement with a widely accepted theoretical approach as well as with numerical device simulation.