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Resistor

A resistor is a component of an electric circuit that produces heat while offering opposition, or resistance, to the flow of electricity. A resistor can introduce resistance into an electric circuit. Resistors are primarily used for protection, operation or current control. Resistors are generally classified into three types which include diffused resistor, polysilicon resistor, and thin film resistor. Thin film resistors generally consist of a thin film of resistive material deposited, such as by sputter deposition, on a layer of insulative material of a substrate. End contacts are formed relative to the resistive material. The performance of thin-film resistors is defined by a number of parameters which include the resistor value, the resistor tolerance, and the temperature coefficient of resistance (TCR). Resistors are commonly used in electronic circuits to inhibit the flow of electric current. Chip resistors are resistors in which a resistance film is coated on a substrate and which is surface mounted on a printed circuit board. A sense resistor is used to sense or measure current flow in an electronic circuit. This measurement can then be used in variety of ways such as to turn off or on other functions in the device. Varistors are resistor elements whose resistance varies in a nonlinear relationship to a change of applied voltage. Zinc oxide varistors are ceramic semiconductor devices based on zinc oxide. They have highly non-linear current/voltage characteristics, similar to back-to-back Zener diodes, but with much greater current and energy handling capabilities.