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?