I am new to this area so please can you keep your answers simple, thanks.
From what I know for an npn transistor in the common-emitter connection the base-emitter junction is in the forward bias and the base-collector junction in the reverse. Electrons flow from the emitter to the base where some leave the base as they recombine with holes, forming the collector current and some pass into the collector forming the collector current. If we increase the base current we get an increase in collector current, why is this?
My first thought would be that the collector current would decrease since more electrons are are flowing into the base electrode rather then the collector electrode. I really am at a loss of how to explain this.
Best Answer
Dave is correct... I'll try to clarify some more.
In an NPN:
BJTs are designed with light doping in the base and a very narrow base width to maximize the diffusion of the emitter current to the collector. As a result, the base current needed to develop the Vbe for a given rate of emitter current injection is very small compared to the emitter and collector current, and so BJTs have high current gain.
Here's an online reference that goes into some detail: Modern Semiconductor Devices for Integrated Circuits, Ch. 8