Transient Response of the Grounded Base Transistor Amplifier with Small Load Impedance

Abstract

An analysis of the transient response of transistor amplifiers necessitates the consideration of transit time effects. Transit time behavior of minority carriers is described by the diffusion equation. Since the diffusion equation applies to minority carriers in the base region of a transistor, a current transfer function may be derived from the diffusion equation relating the collector current to the emitter current. This transfer function is valid only when the transistor is operated as a linear amplifier with small load impedance. For these conditions, the transfer function is solved for the collector current response to a step in emitter current by use of Laplace transform techniques. The collector current rise time, as a function of the α cut-off frequency, is derived from the theoretical equations and compared to measured values.