Varistors

A varistor, also known as a voltage-dependent resistor (VDR), is a two-terminal electronic component that is used to protect circuits from overvoltage transients. It is made of a sintered mixture of zinc oxide particles and other materials, and it has a nonlinear resistance that changes with the applied voltage.

Varistors are used in a variety of applications, including power supply circuits, telecommunications equipment, and automotive electronics. They are often used in conjunction with other protective devices, such as fuses or gas discharge tubes, to provide a robust protection against overvoltage transients.

When the applied voltage across a varistor exceeds a certain threshold level, known as the breakdown voltage, the varistor begins to conduct current. This allows the varistor to divert the transient current away from the protected circuit, limiting the voltage across the circuit and protecting it from damage.

Varistors are commonly used in AC and DC circuits and are available in a range of voltage and current ratings to suit different applications. They are known for their fast response time, high surge current handling capability, and low cost.