Some measurements on commercial transistors and their relation to theory

The effective lifetimes of minority carriers in the bases of five types of transistor have been measured under both steady-state and transient conditions as functions of emitter current. For alloy transistors, good agreement is obtained by the two methods in an overlap range of emitter current, within which both methods are valid. The lower emitter efficiency of the surface-carrier transistor prevents a direct comparison from being made in its case. For three types the effective diffusion constant apparently varies with emitter current over a range somewhat greater than that predicted by existing theory. The variation of base-to-collector current gain with emitter current is discussed in terms of the separate variations of effective lifetime and diffusion constant.