Gain of an NPN Transistor: Understanding Ic/Ib

[Science Proff]

If the base current of an NPN transistor is increased, what will happen to its Collector current since I still don't understand how a transistor amplifies signals or about the current gain. (i.e. Ic/Ib)

 

[yungman]

In very simple terms: It depend on what mode you are in. If you are in linear mode where the collector is still reverse biased, then the collector current is $\beta$ times the base current. If you are running in switch mode where the collector diode is starting to turn on, then increase of base current will just give you slightly lower Vce.

This is from EE point of view, for physics point of view, it is a long story which cover in detail in any of the semi-conductor books.