Transistor behavior at high frequencies

The tee equivalent circuit for junction transistors has been modified to take account of electric field in the base region. This electric field is the result of a graded impurity density in the base region of the transistor. It is shown that a graded base improves the high-frequency performances of the common base stage; however, the improvement in common emitter performance is considerably less because of the increased "excess" phase which accompanies the improved high-frequency performance. The complex hybrid parameters are calculated for the common base and common emitter configurations; these calculations take into account the parasitic interterminal capacities of the transistor. The common emitter calculations are compared to measured data, and substantial agreement is obtained.