I asked this question on electronics.SE but I don't get any good answer may be because its more of a physics question .

I just started reading about transistors from book "Microelectronics circuits"by Sedra/Smith,

This is written in book which I don't understand, any help would be much appreciated

For forward active mode -

"Collector current(Ic) is independent of Vcb(reverse voltage between collector and common base )"

But in next paragraph it is also written that

"saturation current is inversely proportional(Is) to width of base (W) "

And "saturation current (Is) is Directly proportional to collector current (Ic)"

So I concluded that -

collector current (Ic) is inversely proportional to width of base(W)

But how it is possible that collector current (Ic) depends on width of base (W) but not on Vcb?

Isn't by changing Vcb we can change the size of junction (between base and collector) and if size of base-collector junction changes then effective width of base (W) also changes And hence collector current changes?

So why there is contradiction between my conclusion and what is written (as I explained above) in book?

Where did I go wrong?

  • $\begingroup$ And you upload an picture for the IV curve for this device? One must appear in the book. I think that will explain all. $\endgroup$ – boyfarrell Oct 19 '20 at 12:46

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