Higher-order modelling of the diffusion dynamics in a bipolar transistor

A higher‐order diffusion model for a bipolar transistor has been developed. This model is based on the Padé approximation of the quasi‐static expansions of the base and collector currents and gives improved accuracy for the simulation of fast transients and periodic operation at high frequencies. the effect of higher‐order circuit elements on accuracy is demonstrated by calculating the transient response to a step excitation and by determining the scattering parameters of a transistor model with higher‐order elements linearized about an operating point. the higher‐order model is replaced by an equivalent circuit including only conventional elements, and the transient behaviour of these two models is compared.