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You can look at it either way, since Vbe and base current are related by an equation. The transconductance, gm=Ic/Vbe, is very nonlinear (it's exponential). The current gain (Hfe=Ic/Ib) is relatively constant. Also, the input impedance of a common emitter transistor is relatively low, meaning the base voltage changes very little with change in input current. Unless you need a logarithmic transfer function, and some applications do, it is generally much easier to think of the BJT as a current-controlled device.Faiyaz said:Why is a transistor a current controlled device when actually it is the potential across the BE junction that controls the operation of a transistor?
Or am I wrong in making such a statement? :?:
Read my previous post again. You are correct in saying that a bipolar transistor is a voltage-controlled device. You are also correct if you say that it is a current-controlled device.Faiyaz said:Then I am not wrong in stating that a transister is a voltage controlled device?
Although the input impedance may be low, but it is a fact that ultimately it is the VBE that controls the flow of current through the emitter junction which in turn controls collecter current.
Variations in VBE brings about a change in the emitter current. isn't it?
Faiyaz said:Thank you ROn H. For once there is some one who agrees with me. I actually lost a job because of making such a statement.