Base resistance in silicon planar transistors

An examination of the location of the base resistance in silicon planar transistors is followed by an explanation of its variation with current and frequency. It is shown, on the basis of a very simplified mathematical treatment, that at high frequencies the base resistance must be replaced by a complex impedance, the magnitude of which varies inversely as the square root of frequency. Experimental results supporting this conclusion are given, and some of the implications are pointed out.