# Gummel plot

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SiGe HBT Gummel plot

In [electronics](/source/Electronics), the **Gummel plot** is the combined plot of the base and collector [electric currents](/source/Electric_current), I c {\displaystyle I_{\text{c}}} and I b {\displaystyle I_{\text{b}}} , of a [bipolar transistor](/source/Bipolar_junction_transistor) vs. the base–emitter [voltage](/source/Voltage), V be {\displaystyle V_{\text{be}}} , on a semi-[logarithmic scale](/source/Logarithmic_scale). This plot is very useful in device characterization because it reflects on the quality of the emitter–base [junction](/source/Junction_(semiconductor)) while the base–collector bias, V bc {\displaystyle V_{\text{bc}}} , is kept [constant](/source/Constant_(mathematics)).

A number of other device parameters can be garnered either [quantitatively](/source/Quantitative_property) or [qualitatively](/source/Qualitative_data) directly from the Gummel plot:[1]

- The [common-emitter](/source/Common-emitter) current gain, β {\displaystyle \beta } , and the [common-base](/source/Common-base) current gain, α {\displaystyle \alpha } ,

- Base and collector [ideality factors](/source/Ideality_factor), n {\displaystyle n} ,

- Series [resistances](/source/Electrical_resistance) and [leakage currents](/source/Leakage_current).

Sometimes the DC current gain, β {\displaystyle \beta } , is plotted on the same figure as well.

## See also

- [Hermann Gummel](/source/Hermann_Gummel)

- [Bipolar junction transistor](/source/Bipolar_junction_transistor)

- [Gummel–Poon model](/source/Gummel%E2%80%93Poon_model)

## References

1. **[^](#cite_ref-1)** A. S. Zoolfakar et N. A. Shahrol, «Modelling of NPN Bipolar Junction Transistor Characteristics Using Gummel Plot Technique», in 2010 International Conference on Intelligent Systems, Modelling and Simulation (ISMS), 2010, p. 396–400.

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