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Subject: Re: "beta" of transistor

Date: 12/15/00 at 7:50 PM
Posted by: cm
E-mail: tancming@yahoo.com
Message Posted:

In Reply to: Re: "beta" of transistor posted by Alvonzo on 12/15/00 at 6:35 PM:


The transistor's Ib controls the current Ic by the approximate equation Ic=beta*Ib, and this equation usually applies when the transistor is biased on, i.e. its Vbe exceeds the threshold diode voltage of ~0.7V.

Because in BJT, Ib=beta*Ic, it is called a current controlled device. In MOS, Id=beta*W*sq(Vgs-Vth)/(2L) and it is called a voltage controlled device. Ib is equivalent to Vgs and Ic equivalent to Id.

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