In transistor as an amplifier, we have NPN transistor (base in the middle and emitter and collector at the sides). The collector has electrons in majority because it is N-type. similarly, holes are in majority in base, but as it is lightly doped, it has very little amount of hole. Now, when a small signal of alternating current is supplied to the base, the base current changes and this change is called input current. most of this input current moves into the collector (base has less holes so most of the current moves on when it fills the holes). Now, the collector has its own majority charge carriers (electrons) and some more electrons are added to it by the input signal. So when collector gives current to the load, it will be the combination of input signal and the already present electrons. Hence, small signal is amplified.
Am I right or wrong?
Best Answer
You have got the 'amplification' idea wrong.You may add thousands and thousands of electrons to the input signal. But if 'CHANGES' are of same value as input signal , you do not have amplification. You have just changed the voltage level.
The question is not very clear. For example it is not clear what configuration you refer to. I assume you have the common emitter configuration of npn transistor in mind.
The transistor amplifies the 'CHANGES' in signal. Think of the BASE as a sort of 'CONTROL'. For npn transistor, the base signal changes number of holes available. You can imagine that the base that controls the resistance between emitter and collector.
(Hint: TRANSISTOR = TRANSFER + RESISTANCE)
A base signal changes the current flowing through emitter collector terminals. By controlling the amount of current/electrons that flows between emitter and collector in a manner proportional to the input current you get amplification.