A study of the effect of peripheral injection in bipolar transistors using simplified computer analysis

The effect of injection from the emitter periphery into the base of a double diffused bipolar transistor is studied using the variable boundary regional approach and representing minority carrier current as the sum of radial currents using the cylindrical approximation. The results are combined with those for the active base region (i.e. under the emitter). It is shown that improvement in the prediction of h
FE
and f
T
versus I
c
is obtained by inclusion of the charge and current in the peripheral base region. The method used has the advantage of 1) fast computer time and 2) separation of active and peripheral base region and provides a useful tool to improve the precision when designing devices from fabrication data.