Orthogonal functions

In electronics, the Gummel plot is the combined plot of the base and collector electric currents, $I_{c}$ and $I_{b}$, of a bipolar transistor vs. the base-emitter voltage, $V_{be}$, 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, $V_{bc}$, is kept at a constant.

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

• 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.

SiGe HBT Gummel Plot

See also

• Hermann Gummel
• Bipolar junction transistor

References

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