Application Aspects of the Germanium Diffused Base Transistor

This paper briefly considers some of the improvements in transistor circuit performance made possible by the diffused base germanium transistor developed at the Bell Telephone Laboratories. The paper points out the advantage of the diffusion process for the fabrication of the thin base layers required for very high frequency transistors. The basic steps in the fabrication of a germanium transistor with a base-layer thickness of
1.5 \times 10^{-4}
centimeters and an alpha-cutoff frequency of 500 megacycles per second are given. The electrical equivalent circuit of this transistor and the current gain frequency characteristics in both the common emitter and common base connections are presented and discussed. The potential of this type transistor for performing various circuit functions in both the common emitter and common base connections are then briefly discussed. The various application possibilities discussed are based on both the measured electrical characteristics of the transistor and the actual performance characteristics of research and advanced development models of diffused base transistors in exploratory circuits. The greater universality of application of the diffused base transistor as compared to earlier transistors is briefly discussed.