On the Variation of Transistor Small-Signal Parameters with Emitter Current and Collector Voltage†

Abstract

The variation of transistor small-signal parameters as a function of emitter current and collector voltage has been investigated theoretically and the results have been compared with those of a parallel experimental investigation. The experimentally determined variations of the low frequency hybrid parameters have been found to be in excellent agreement with the calculations, apart from the variation of h₁₂ with emitter current, which showed a quantitative disagreement with the theory. Misawa's theoretical expression for the cut-off frequency, fα, has been compared with the experimental results and has been found to lead to a wrong dependence on the emitter current.