Effects of bias and load conditions on dynamic self-heating of bipolar transistors

Frequency dispersion due to dynamic self heating in small-signal common-emitter voltage gain of bipolar transistors was modelled and characterized. The gain was found to either increase or decrease with frequency depending on the bias and load conditions. Both distributed and lumped models could explain the observed dispersive behavior and provide reasonable fit to measured data. However, the time constants extracted by using the lumped model may not have physical significance.