Varistor

The Varistor is a passive two-terminal solid-state semiconductor device with an electrical resistivity that varies with applied voltage. In electrical and electronic circuits, varistors are used to provide optimal operating conditions or protect the circuits against excessive transient voltages. Unlike fuse and circuit breaker that protect the circuit from over-current, the varistor protects the circuit from over-voltage. Varistor blogs further current flow once the voltage reaches its clamping voltage (maximum limit). The varistor changes its resistance value automatically with the change in voltage across it making it a voltage-dependant, nonlinear resistor or VDR for short.

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