Transistor parameters in the avalanche mode

While the literature is quite complete on transistor parameters below the avalanche region and a considerable amount of work has been directed to the region where complete breakdown occurs, the intermediate region has received very little study. This paper deals with the behaviour of the transistor in the border region of avalanche and particularly treats transistors of very high cut-off frequency. This is done in terms of the general four-terminal network parameters. The effects of avalanche on the a cut-off frequency and the maximum frequency of oscillation are discussed by using the admittance parameters and the short circuit current gain,which were measured experimentally. Further, it is shown that operation under avalanche conditions can extend the maximum useful operating frequency