Low-temperature (77 K) BJT model with temperature dependences on the injected condition and base resistance

A low-temperature (77-K) bipolar transistor model based on physical analysis by considering the temperature dependences of the injection condition and base resistance modulation is described. A charge-based injection factor which describes the temperature dependence of the ideality factor n is introduced by taking into account the electron and hole concentration ratios at the edges of the emitter-base depletion layer. The temperature dependence of base resistance modulation is explained by using the temperature dependences of the conductivity modulation effect, the base pushout effect, and the emitter current-crowding effect. Calculations using the model are compared with measurements, revealing excellent agreement over a wide temperature range from 50 to 298 K.<
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