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How do you calculate the current gain of a transistor?


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2009-09-01 22:45:52
2009-09-01 22:45:52

Bipolar transistor current gain is also called "Beta," or the h-parameter "hfe."

beta = current_out / current_in

The beta of a BJT is mostly determined by the thickness of the Base region, and by the excess doping in the Emitter relative to the Base. A thin Base and a heavily-doped Emitter leads to a high value for current gain.

In a BJT, beta = Ic / Ib In a FET, beta is usually taken as infinity, since no current flows in or out of the gate. Beta is an impirical number. It means nothing unless the Ic is known or the load. It can have a beta from 1000 to 10 it all depends on the load.

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