Question

What is meant by amplification? Draw a simple circuit of n-p-n common emitter transistor amplifier.
On the basis of band theory, distinguish between conductor, insulator and semi-conductor.

Answer 1

Amplification refers to increasing the amplitude and hence the output power of a signal. This is carried out by an amplifier.

An circuit of n-p-n common emitter transistor amplifier is shown in figure above.

Insulators do not conduct electricity which is due to large spacing between conduction and valence bands in them.

Semiconductors have conductivity between insulators and conductors, which is because of very small gap between the two bands.

Conductors have an overlap of conduction and valence band, and hence they easily conduct all the electron present in their valence shells.