Gummel plot

In <a href="/facts/Electronics/E4JhgISq">electronics</a>, the Gummel plot is the combined plot of the base and collector <a href="/facts/Electric_current/Dc1xdnUX">electric currents</a>, 
 
 
 
 
 I
 
 c
 
 
 
 
 {\displaystyle I_{\text{c}}}
 
 and 
 
 
 
 
 I
 
 b
 
 
 
 
 {\displaystyle I_{\text{b}}}
 
, of a <a href="/facts/Bipolar_junction_transistor/9BMcGv5Q">bipolar transistor</a> vs. the base–emitter <a href="/facts/Voltage/EN2po6N2">voltage</a>, 
 
 
 
 
 V
 
 be
 
 
 
 
 {\displaystyle V_{\text{be}}}
 
, on a semi-<a href="/facts/Logarithmic_scale/CvIGK5TQ">logarithmic scale</a>. This plot is very useful in device characterization because it reflects on the quality of the emitter–base <a href="/facts/Junction_(semiconductor)/817HaCWJ">junction</a> while the base–collector bias, 
 
 
 
 
 V
 
 bc
 
 
 
 
 {\displaystyle V_{\text{bc}}}
 
, is kept <a href="/facts/Constant_(mathematics)/SxlxTWFT">constant</a>.
A number of other device parameters can be garnered either <a href="/facts/Quantitative_property/C1t5h075">quantitatively</a> or <a href="/facts/Qualitative_data/1F9eR1WP">qualitatively</a> directly from the Gummel plot:

<ul><li>The <a href="/facts/Common-emitter/GBVl6DPa">common-emitter</a> current gain, 
 
 
 
 β
 
 
 {\displaystyle \beta }
 
, and the <a href="/facts/Common-base/KK7aHT5e">common-base</a> current gain, 
 
 
 
 α
 
 
 {\displaystyle \alpha }
 
,</li>
<li>Base and collector <a href="/facts/Ideality_factor/3wx4F0Aw">ideality factors</a>, 
 
 
 
 n
 
 
 {\displaystyle n}
 
,</li>
<li>Series <a href="/facts/Electrical_resistance/hxSt0UAj">resistances</a> and <a href="/facts/Leakage_current/Nd6PNxhV">leakage currents</a>.</li></ul>
Sometimes the DC current gain, 
 
 
 
 β
 
 
 {\displaystyle \beta }
 
, is plotted on the same figure as well.

Gummel plot open-in-new

Gummel plot