Method for determining the emitter and base series resistances of bipolar transistors

A simple method for determining both the emitter and the base series resistances of bipolar transistors from the measured I - V characteristics is described. The method is based on the observation that deviation of the base current from the ideal
\exp (qV_{BE}/kT)
behavior at high currents can be attributed solely and relatively simply to series resistances. Series resistances determined by this method are given for sample high-speed digital bipolar transistors.