Junction Transistor Short-Circuit Current Gain and Phase Determination

This paper presents a physical analysis which establishes that the phase shift associated with the common-base current gain of a junction transistor is of the type defined by Bode as "minimum." The phase of the common-base current gain is therefore uniquely determined by its magnitude characteristic. Using the minimum phase properties of networks and the empirically observed behavior of transistor current gain, it is shown that the complete common-base and common-emitter current-gain magnitude and phase frequency characteristics can be determined from three amplitude measurements, namely the low frequency ¿, ¿0, the magnitude of the common-emitter current gain at a single frequency in the common-emitter cutoff region, and the common-base cutoff frequency f¿. The paper develops the equations for determining the common-emitter and common-base short-circuit current gains from these three magnitude measurements.