What is the function of a varistor?

The function of a varistor is to protect a circuit from transient voltages. Varistors, also known as voltage-dependent resistors (VDRs), are semiconductor devices that exhibit a nonlinear resistance in relation to the voltage applied across them. When the voltage exceeds a certain threshold, the resistance of the varistor decreases significantly, allowing it to conduct current and effectively divert excessive voltage away from sensitive components in an electrical circuit. This action helps to prevent damage from voltage spikes, such as those caused by lightning strikes or electrical switching.

The nature of a varistor allows it to respond quickly to high-voltage transients, making it an essential component in surge protection devices and power strips. Its ability to clamp voltage and decrease resistance plays a crucial role in safeguarding electronic equipment from damaging surges, thereby enhancing the reliability and longevity of the devices it protects.