Two-Dimensional Current Flow in Junction Transistors at High Frequencies

The effect of two-dimensional current flow in a junction transistor at high frequencies is analyzed, with particular emphasis on the rectangular geometry employed for grown-junction transistors. At high frequencies, the distributed nature of the base region must be taken into account in general. For example, in the usual equivalent circuit for the transistor, the ohmic base resistance rb¿ must be replaced in general by a complex base impedance, which decreases in magnitude with increasing frequency as a result of a high-frequency internal biasing effect. The effect of this modification upon circuit performance is discussed, and transistor design considerations are outlined briefly. An approximate distributed model is used for the analysis, but it is shown in Appendix II that the solutions thus obtained are consistent with the equations governing twodimensional current flow in a semiconductor region.