Varistor is the abbreviation of voltage sensitive resistor, and it is a kind of non-linear resistance element. The resistance of the varistor is related to the voltage applied at both ends. When the voltage applied to the varistor is within its nominal value, the resistance of the resistor presents an infinite state, and almost no current flows. When the voltage at both ends is slightly greater than the nominal voltage, the varistor quickly breaks down and conducts, and its resistance drops quickly, making the resistor in a conducting state. When the voltage drops below the nominal voltage, its resistance starts to increase again and returns to a high resistance state. When the voltage at both ends exceeds its maximum limit voltage, it will be completely broken down and damaged, unable to recover by itself.

The varistor has excellent performance and low price, small size, wide operating voltage range, fast response to overvoltage pulse, strong inrush current resistance, low leakage current (less than a few microamps to tens of microamps), and temperature coefficient of resistance Small and other characteristics, it is an ideal protection component, widely used in home appliances and other electronic products, often used to form over-voltage protection circuit, noise elimination circuit, spark elimination circuit, lightning protection circuit, surge voltage Absorption circuit and protection of semiconductor components.