Resistors are the most widely used components in electronic circuits. They are usually divided into different series according to power and resistance values and selected by the designers of power supply circuits. The resistor in the circuit is mainly used to adjust and stabilize the current and voltage, can be used as a shunt and voltage divider, but also for the circuit to match the load.

According to the requirements of the circuit, it can also be used to amplify the negative feedback or positive feedback circuit, voltage-current conversion, input overload voltage or current protection components, and can be composed of RC circuit as oscillating, filtering, bypass, differential, integral and time constant components.

There are many types of fixed resistors. The resistor of which kind of material and structure should be selected according to the specific requirements of the application circuit.

For high frequency circuits, non-wire-wound resistors with small distributed inductance and capacitance should be selected, such as carbon film resistors, metal resistors and metal oxide film resistors. Low noise resistors, such as metal film resistors, carbon film resistors and wire-wound resistors, should be used for high gain small signal amplifiers, rather than synthetic carbon film resistors and organic solid resistors with higher noise.

Wire-wound resistors have high power, low current noise, high temperature resistance, but large size. Ordinary wire-wound resistors are commonly used in low-frequency circuits or as current limiting resistors, divider resistors, drain resistors, or bias resistors for high-power pipes.

High-precision wire-wound resistors are widely used in fixed attenuators, resistance boxes, computers and various precision electronic instruments.

The resistance value of the selected resistor should be close to a nominal value of the calculated value in the application circuit. Standard series resistors should be preferred.

The error of resistors used in general circuits is ±5~±10. Precise instrument and the resistor used in special circuit, should choose precise resistor.