Draw the voltage current characteristics of a$pn$ -junction and compare it with characteristic of resistor. 

Distinguish between $n$ -type  and $p$-type semiconductor on the basis of energy band diagram. Explain the process of conduction in both types of material.

What is meant by the term ‘doping’ of an intrinsic semiconductor? How does it affect the conductivity of a semiconductor?

Draw the current versus voltage characteristic curve of a Zener diode. Indicate the position of Zener voltage. Draw a labelled circuit diagram of a dc voltage regulator using a Zener diode.