What Is A Varistor

"Varistor" is a type of resistor device with nonlinear volt ampere characteristics, mainly used for voltage clamping in circuits under overvoltage, absorbing excess current to protect sensitive devices. Its English name is "Voltage Dependent Resistor", abbreviated as "VDR" or "Varistor". The material of the resistor body of a varistor is semiconductor, so it is a variety of semiconductor resistors. The widely used "zinc oxide" nowadays (ZnO) varistor, its main material consists of divalent element zinc (Zn) and hexavalent element oxygen (O). So from a material perspective, zinc oxide varistors are a type of II-VI group oxide semiconductor. In Taiwan, China, China, varistors are called "surge absorbers", sometimes also called "electric shock (surge) suppressors (absorbers)".

Varistor is a voltage limiting protective device. By utilizing the nonlinear characteristics of varistors, when overvoltage occurs between the two poles of the varistor, the varistor can clamp the voltage to a relatively fixed voltage value, thereby achieving protection for the subsequent circuit. The main parameters of a varistor include: varistor voltage, current capacity, junction capacitance, response time, etc.

The response time of varistors is in the ns range, faster than gas discharge tubes and slightly slower than TVS tubes. Generally, their response speed can meet the requirements for overvoltage protection in electronic circuits. The junction capacitance of varistors is generally in the range of several hundred to several thousand Pf, and in many cases, it is not suitable to be directly applied in the protection of high-frequency signal lines. When applied in the protection of AC circuits, because its junction capacitance can increase leakage current, it needs to be fully considered when designing protective circuits. The flow capacity of a varistor is larger, but smaller than that of a gas discharge tube. Varistor, abbreviated as VDR, is a nonlinear overvoltage protection semiconductor component that is sensitive to voltage.