Effect of Base-Contact Overlap and Parasitic Capacities on Small-Signal Parameters of Junction Transistors

In a grown-junction transistor in which the base connection consists of an alloy contact, overlap on emitter and/or collector regions may produce appreciable capacity between emitter-base and collector-base terminals. The effect of such overlap capacity upon measured small-signal parameters at high frequencies is described briefly for both grounded-base and grounded-emitter operation. Typical experimental results are shown for two different parameters. Also, it is noted that interterminal parasitic capacities affect measured parameters in the same manner as do these overlap capacities.