Varistors
Varistor stands for Variable Resistor. It is a voltage nonlinear resistor/voltage-dependent resistor. It is an element that changes its resistance value depending on applied voltage. This feature is mostly used to protect electronic devices from the abnormal voltage, such as lightning surge and static electricity. Unlike thermistors it has no practical time delay of its function.
Varistor resistor is a resistive device with non-linear volt-ampere characteristics. It is mainly used for voltage clamping when the circuit is subjected to overvoltage and absorbs excess current to protect sensitive devices, and its full English name is "Voltage Dependent Resistor", abbreviated as "VDR", or "Varistor".
Varistor’s are voltage dependent, nonlinear devices which have an electrical behavior similar to back-to-back zener diodes. Zinc oxide varistors are nonlinear resistors, consisting mainly of zinc oxide and several kinds of metal oxide additives. They are bilateral and symmetrical V-1 characteristics curve and unparalleled large peak current capabilities are used for absorption of transient voltage, suppression of pulse noise and circuit voltage stabilization.
Features
• Fast response
• Excellent voltage ratio
• High stabilization for circuit voltage
• Unparalleled absorption for transient voltage characteristics
• Bilateral and symmetrical V-1 characteristics curve
Applications
• Surge Protection in consumer electronics
– industrial electronics
– telephone and telecommunication systems
– automobile equipment
– measuring and controller systems
– electronic home appliances
– gas and petroleum appliances
• Absorption of switching surge from various kinds of relays
and electro-magnetic valves.
• Electrostatic discharge and spike noise suppression.
• Protection of various kinds of transistors, diodes, ICs,
thyristors, triac semiconductors, etc.
• Automobile control system such as transistorized