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MODELING OF BIPOLAR TRANSISTOR TURNOFF (SECOND BREAKDOWN, FINITE-DIFFERENCE METHOD, POWER)
An isothermal, two-dimensional numerical calculation of the potential and current distribution in an n('+)-p-n-n('+) bipolar power transistor driving an inductive load during its turnoff transient has been carried out. The transistor is initially considered to be in a heavily saturated 'on' state and is then turned off by extracting a constant base current. The simulation shows that during the turnoff transient, current constriction to the center of the emitter together with the increasing collector-emitter voltage produces a high electric field near the collector n-n('+) junction which can initiate avalanche injection. It has been found that the collector current density is not uniform vertically (from collector to emitter) due to the current spread-out in the collector n-region. Previous one-dimensional analytical analyses of second breakdown did not consider this important effect. Thus, for an accurate prediction of reverse second breakdown voltage, the two-dimensional current flow should be considered. ^
HWANG, KYUWOON, "MODELING OF BIPOLAR TRANSISTOR TURNOFF (SECOND BREAKDOWN, FINITE-DIFFERENCE METHOD, POWER)" (1986). Doctoral Dissertations Available from Proquest. AAI8622680.