Question

Write one main use of Zener diode.

Answer 1

Hint: One of the special properties of a Zener diode includes the fact it can maintain a constant value of voltage across itself for any value of the input voltage supplied across it. This property of Zener diodes allows us to use it as a voltage regulator in electrical circuits.

Complete step-by-step answer:
Zener diode is a type of p-n junction diode made of semiconducting materials. It is a type of diode which is heavily doped and can be used in the reverse biased condition without undergoing breakdown. When a Zener diode is reverse biased then it is observed that it maintains a fixed voltage about itself, irrespective of the large input voltages fed to it. This fixed voltage is equal to the zener breakdown voltage of the zener diode used in the circuit. This means that we can use the zener diode to regulate the voltage in a circuit in which voltages are fluctuating. The use of zener diodes will ensure that the voltage remains constant across a given load irrespective of the change in the input voltage of the circuit. The following circuit diagram shows how a zener diode can be used as a voltage regulator. Here an unregulated input voltage is fed to a zener diode through a resistance ${R_S}$. Since, voltage remains the same in parallel combination, we attach the load resistance ${R_L}$ in parallel with the zener diode which gives a fixed output voltage equal to the zener breakdown voltage ${V_Z}$.

Note: 1. If we forward bias a zener diode, then it will act as any normal p-n junction diode. So, the zener diode plays a role only when it is used in reverse biased condition.
2. This property of zener diode can also be used to protect electronic instruments in a circuit where the fluctuating voltages may damage the instrument.