Question

It is often said that the transistor is a basic element of amplification, yet it supplies no energy of its own. Exactly what is its role in amplification?

Short answer

The role of the transistor in the amplifier is to split the input current into a tiny current flowing out of the base and a huge fraction flowing out of the collector.

Step-by-step solution

A concept:

The first N-type semiconductor from the left is called the emitter. The middle P-type semiconductor is called the base and the N-type end semiconductor is called the collector. The output circuit to drive the speaker is connected between the collector and emitter ends.

Role in amplification:

The input introduces minute voltage changes in the emitter-base, which changes the rate proportionally the electron flow into the base from the emitter.

A small fraction of the varying current becomes the circulating input current and the remainder becomes a proportional varying current in the output circuit.

Therefore, the transistor thus amplifies the variation in the input current.