HIGH FREQUENCY RESPONSE OF A BIPOLAR JUNCTION TRANSISTOR.

The frequency capability of a bipolar junction transistor can be specified in terms of its transition frequency, f//T, which in turn is related to the frequency f//B, at which the forward current transfer ratio (h//f//e) is down 3 db. The value of f//B results in a pole in the complex frequency variable s-plane, whose location with respect to the poles of the circuit time constants then determines the resultant frequency response of the transistor in its circuit configuration. The poles related to the circuit time constants are simply found by defining the driving point resistance which are shunted by the energy storage elements.