The current gains of diffusion and drift types of junction transistors

Theoretical aspects of the frequency dependence of current gain are reviewed. A semi-empirical expression for the common-base internal current gain ¿d is given, which closely approximates to the theoretical expression and is useful for analytical work. Measurements of the complex common-base external current gain ¿, from which ¿d is derived, are presented for frequencies up to 210 Mc/s. A comparison of the complex loci of ¿d with theoretical loci shows good agreement in most cases. A simple method of estimating the relative drift potential across the base of drift transistors is discussed, and two methods of determining the emitter depletion-layer capacitance are described.