Question

Zener diode is used for
A. Amplification
B. rectification
C. Stabilisation
D. All of the above

Answer 1

A zener diode is highly doped p-n junction which is not damaged by high reverse current. It has a very sharp breakdown voltage. Therefore, in reverse biased condition, the voltage across the diode is constant for a wide range of current.

Complete answer:
A Zener diode is a special type of diode. It is a highly doped p-n junction diode which is not damaged by high reverse current. Reverse current is the current which creates a voltage across the diode such that the diode becomes reversed biased. When the diode is in the state of reverse bias, it anode is at lower potential than that of its cathode.

When a diode is reverse biased, no or very less current flows through the diode. However, if the reverse voltage is increased by a large amount, the diode breaks down and a large amount of current flows through the diode. This voltage is called the breakdown voltage of the diode.

A zener diode has a very sharp breakdown voltage. Therefore, in reverse biased condition, the voltage across the diode is constant for a wide range of current. This feature of the diode can be used as a voltage regulator.

In a voltage regulator, a zener diode is connected in parallel to the load. The input voltage is such that the diode is in the reverse biased condition. Hence, the voltage across the diode remains constant and thus the voltage across the load remains constant. Therefore, we can say that a Zener diode can be used for stabilisation of the voltage across a load.

Hence, the correct option is C.

Note: Zener diode can be used as a voltage regulator only when it is connected across the load in reverse biased condition. This is because the voltage across the zener diode is constant only in reverse biased condition. The voltage in forward bias increases with the current.