HIGHER-ORDER MODELING 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 Pade 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.