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In electronics, the Gummel plot is the combined plot of the base and collector electric currents, $I_{\text{c}}$ and $I_{\text{b}}$, of a bipolar transistor vs. the base–emitter voltage, $V_{\text{be}}$, on a semi-logarithmic scale. This plot is very useful in device characterization because it reflects on the quality of the emitter–base junction while the base–collector bias, $V_{\text{bc}}$, is kept constant.

A number of other device parameters can be garnered either quantitatively or qualitatively directly from the Gummel plot:^[1]

• The common-emitter current gain, $\beta$, and the common-base current gain, $\alpha$,
• Base and collector ideality factors, $n$,
• Series resistances and leakage currents.

Sometimes the DC current gain, $\beta$, is plotted on the same figure as well.

• Hermann Gummel
• Bipolar junction transistor
• Gummel–Poon model