Gummel plot: A design and modeling utility for bipolar design

Gummel plots are a very useful utility that a bipolar fabrication facility provides or can provide. This is a great utility/tool for the bipolar IC designer. In addition to actual device models and layout rules Gummel plots serve to provide, at a glance the DC performance of a bipolar. The plot itself is a semi-logarithmic plot of the collector current and the base current versus the Vbe of the device. From these plots a number of parameters can be estimated very quickly and can be of inestimable value to the designer. Obviously DC forward gain ( Ic/Ib), is clearly shown, the Vbe of the device at current is available, the common base current gain is available in a straightforward manner and the DC gm can be estimated among other parameters.