Resistors are one of the most widely used electronic components in electronic devices. It accounts for more than 30% of the total number of components in electronic equipment. The role of resistors is mainly used to adjust the current and voltage in the circuit. That is to play the role of step-down, current limiting, shunt, isolation, waveform transformation, matching and signal amplitude adjustment, etc. The measurement unit of the resistor is ohm. The letter R is often marked in the circuit. So how many resistor classifications are there?

There are different classification methods for resistors, depending on the materials used to make them, their structures, and how they are used in circuits. Generally, resistors are divided into two categories: fixed resistors and variable resistors according to their resistance values. A resistor with a fixed resistance is called a fixed resistor. Commonly referred to as "resistor". A resistor whose resistance value can be continuously adjusted manually within a certain range is called an adjustable resistor or potentiometer. After the internal resistance of the electronic device is adjusted, it is called adjustable resistance that does not need to be adjusted by the user. The ones installed on the control panel that can be adjusted by the user are called potentiometers. In addition, there is a class of semiconductor resistors. For special purpose resistors.

According to different materials, resistors can be divided into wire wound resistors, film resistors (further divided into carbon film resistors and metal oxide film resistors), carbon resistors, etc.

According to different uses, resistors can be divided into precision resistors, high-frequency resistors, high-voltage resistors, high-power resistors, low-power resistors, thermistors, fuse resistors (fuse resistors), varistors, photoresistors and gas-sensitive resistors.

According to the different lead-out electrodes, the resistance can be divided into axial lead resistance and leadless resistance (chip resistance).

1. Carbon film resistors

Carbon film resistors are the earliest and most widely used resistors, which are made by depositing carbon on a porcelain substrate. By changing the length and thickness of the carbon film, carbon film resistors with different resistance values ​​can be made. It is characterized by high precision, good high frequency characteristics, and good temperature characteristics (when the ambient temperature changes, the resistance value changes very little), commonly used in instruments Among other high-end equipment, it is used the most in general equipment. The most commonly used color ring resistors in practical circuits are a kind of carbon film resistors.

2. Metal oxide film resistors

Metal oxide film resistors are made by depositing a layer of alloy powder on the porcelain base under vacuum conditions. Its main features are high precision and good stability, and it is not easy to distinguish from carbon film resistors in appearance.

3. Wirewound Resistors

Wirewound resistors are made of constantan wire or manganese copper wire wound on the insulating skeleton. It is characterized by high temperature resistance, high precision and high power. Common wirewound resistors include cement resistors, insurance resistors, etc.

The fuse resistor has a dual function. It has the electrical characteristics of ordinary resistors under normal conditions. But when the current flowing through the fuse resistor exceeds its allowable value. The fuse resistor will fuse within the specified time and cut off the power supply, so as to achieve the purpose of protecting the power supply. Fuse resistors are often marked with RF or FOOO in circuits, and their appearance is similar to that of metal oxide film resistors.

4. Integrated resistor assembly

An integrated resistor device, also known as a resistor bank, is to encapsulate multiple resistors with the same resistance value together to form a whole. It is a resistor network with regularization, small size and stable performance. Commonly used in high-end complex electronic equipment such as computers. The integrated resistance device in the actual circuit is often marked with RN.

5. No lead resistance

Leadless resistors, also known as chip resistors, are resistors without leads. They are directly welded on the circuit board. Chip resistors are often used in complex circuits and small-volume devices, such as computer motherboards, liquid crystal displays, and projectors.

6. Adjustable resistance

The small adjustable resistor used to adjust the working point inside the machine is generally called an adjustable resistor, and its resistance value cannot be adjusted outside the machine, and is often marked with VR. Used on the control panel of the equipment, the resistor whose resistance value can be adjusted by the user is generally called a potentiometer, which is often marked with W.

7. Varistor

A varistor is a resistor that is sensitive to voltage and is a semiconductor device. Its production material is mainly vaporized zinc. Its resistance value is close to infinity under normal circumstances. When the voltage across the varistor reaches or exceeds its critical point, its internal resistance decreases sharply and cannot be recovered, a phenomenon called "breakdown".

Varistors are mainly used at the AC input end of electrical equipment for overvoltage protection. When the input voltage is too high, its resistance will decrease. The fuse connected in series in the input circuit is blown to cut off the input, thereby protecting the electrical equipment.

8. Thermistor

A thermistor is a resistance device whose resistance value can change with temperature, and has different functions in different application environments. Mainly used for temperature detection and current limiting in electronic circuits. The thermistor is divided into positive temperature coefficient thermistor (PTC thermistor for short) and negative temperature coefficient thermistor (NTC thermistor for short) according to the different temperature coefficients.

PTC (Positive Temperarture Coefficient), which means positive temperature coefficient, generally refers to semiconductor materials with a large positive temperature coefficient. Before the temperature of the PTC thermistor rises to a certain point, its resistance increases slowly with the temperature, and when it reaches this certain temperature point, its resistance increases sharply (this certain temperature point is called the Curie point). PTC thermistors are widely used in household appliances, such as refrigerators, color TVs, and CRT monitors. PTC thermistors are often used as degaussing resistors in monitors and color TVs.

NTC (Negative Temperature Coefficient), which means negative temperature coefficient, generally refers to semiconductor materials or components with a large negative temperature coefficient. The so-called NTC thermistor is a negative temperature coefficient thermistor. When the temperature is low, its resistance value is higher; as the temperature increases, the resistance value decreases. NTC thermistors are often used in power supply circuits to suppress inrush current at the moment of startup.

Thermistors are special-purpose resistors, and in addition, there are other special resistors. Such as photoresistors, gas-sensitive resistors, humidity-sensitive resistors, etc.

The above is the classification of resistors, I hope to help everyone.