Characterization and measurement of the base and emitter resistances of bipolar transistors

Most previously published methods of measuring transistor base resistance are surveyed and compared. The input impedance circle diagram method is examined in detail and correction factors due to parasitic capacitances are derived. Emitter series resistance is also estimated from this data. A new method of measuring base resistance requiring much less measurement effort is introduced and shown to give good agreement with the circle diagram method. This method is called the phase cancellation method and gives an estimate of base resistance from the common base input impedance at the collector current where its imaginary part is zero. Also an estimate of series emitter resistance is obtained from this measurement and shown to agree well with other methods.