A varistor is an essential component used to protect electronic circuits from voltage surges or spikes.

In electronic circuits, voltage surges and spikes can damage components and may even lead to complete circuit failure. A varistor, also referred to as a voltage-dependent resistor (VDR), is specifically designed to safeguard against these harmful voltage fluctuations.

The construction of a varistor involves a material that exhibits a non-linear resistance characteristic. This means that its resistance varies with the voltage applied across it. At low voltage levels, the varistor maintains a high resistance. However, as the voltage increases, its resistance decreases significantly. When a voltage surge or spike occurs, the resistance of the varistor drops sharply, allowing it to absorb the excess voltage and protect the rest of the circuit from potential damage.

Varistors are widely utilized in power supplies, surge protectors, and various electronic devices that may be vulnerable to voltage surges. Additionally, they are employed in lightning arresters to safeguard buildings and structures from the impact of lightning strikes.

In summary, the primary function of a varistor in an electronic circuit is to protect against voltage surges or spikes that could harm components. By absorbing excess voltage, the varistor helps ensure the safe and reliable operation of electronic devices.