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(3) When the collector is open and a specified reverse voltage is applied between the emitter and base, the current at the emitter is actually the reverse saturation current at the emitter junction.transistor

(4) The DC current amplification factor β 1 (or hEF) refers to the ratio of the DC current output by the collector to the DC current input by the base when there is no AC signal input in the common emitter connection,transistor  that is:

β1=Ic/Ib

2. Communication parameters

(1) The AC current amplification factor β (or hfe) refers to the ratio of the change in collector output current △ Ic to the change in base input current △ Ib in the common emitter connection, that is:

β=△Ic/△Ib

The beta of a typical transistor is approximately between 10-200. html "target=" -blank "title=" 10-200 ">10-200. If the beta is too small, the current amplification effect is poor. If the beta is too large, although the current amplification effect is large, the performance is often unstable.

(2) The common base AC amplification factor α (or hfb) refers to the ratio of the change in collector output current △ Ic to the change in emitter current △ Ie when connected in a common base configuration, that is:transistor

α=△Ic/△Ie

Because Δ Ic<Δ Ie, therefore α<1. If the alpha value of the high-frequency transistor is greater than 0.90, it can be used

The relationship between alpha and beta:transistor