## What is the symbol of a varistor? Is it in series in the circuit or in parallel in the circuit?

Varistor is a voltage-limiting protection device. It utilizes the non-linear characteristics of the varistor. When an overvoltage appears between the two poles of the varistor, it can clamp the voltage to a relatively fixed voltage value, thereby realizing the protection of the subsequent circuit. The main parameters of varistor are: varistor voltage, current capacity, junction capacitance, response time, etc.

The working principle of 　　 varistor is roughly divided into the following two types:
① When a varistor is under pressure or the voltage is lower than its threshold, the current flowing through it is the smallest, which is equivalent to a resistance of infinite resistance. In other words, when the voltage applied to the resistor is lower than its threshold, the resistor is similar to an off-state switch.
②When the voltage applied to the resistor exceeds its threshold, the current flowing through it increases by a factor of two, which is equivalent to a resistor with infinite resistance. In other words, when the voltage applied to it is higher than its threshold, it is equivalent to a closed switch.

What is the symbol of varistor
“Variator” is a resistive device with nonlinear volt-ampere characteristics. It is mainly used to clamp the voltage when the circuit is subjected to overvoltage and absorb excess current to protect sensitive devices. The English name is “Voltage Dependent Resistor” abbreviated as “VDR”, or “Varistor”.