The role of fixed resistors

The resistance value of a fixed resistor is fixed, and the resistance value is its nominal resistance value. Due to its wide range of uses, there are many types of fixed resistors, which are generally classified according to their constituent materials and structural forms.

1. What is a fixed resistor

Fixed resistors are generally directly referred to as resistors in daily life. It is a current limiting component. After connecting the resistor in the circuit, the resistance value of the resistor is fixed, usually two pins, which can limit the current through the branch connected to it. A resistor whose resistance cannot be changed is called a fixed resistor. Variable resistance is called potentiometer or variable resistor . An ideal resistor is linear, that is, the instantaneous current through the resistor is proportional to the applied instantaneous voltage. Variable resistor for voltage divider.

2. Fixed resistor features

The terminal voltage and current have a definite functional relationship, and the two-terminal device that reflects the ability to convert electrical energy into other forms is represented by the letter R, and the unit is ohms. Actual devices such as light bulbs, heating wires , resistors, etc. can be represented as resistor elements.


The resistance value of a resistive element is generally related to temperature, material, length, and cross-sectional area. The physical quantity that measures the degree of resistance affected by temperature is the temperature coefficient, which is defined as the percentage of the resistance value that changes when the temperature increases by 1°C. The main physical feature of a resistor is to convert electrical energy into thermal energy. It can also be said that it is an energy-consuming element, and the current passes through it to generate internal energy. Resistors usually play the role of voltage divider and current shunt in the circuit. For signals, both AC and DC signals can pass through resistors.

3. The role of fixed resistors

It is made of constantan or nickel-chromium alloy resistance wire wound on a ceramic skeleton. There are two types of resistors, fixed and variable. It is characterized by stable operation, good heat resistance, small error range, and can withstand large instantaneous peak power. Its rated power is generally above 1w, can withstand high temperature, and can still work normally at an ambient temperature of 170 °C. But it is large in size and low in resistance, mostly below 100KΩ. Due to structural reasons, its distributed capacitance and inductance are relatively large and cannot be applied to high-frequency circuits. This type of resistor is usually used as a step-down or load in high-power circuits.

Metal oxide film resistors are formed by decomposing and depositing hydrolyzable metal salt solutions (such as tin tetrachloride and antimony chloride) on the surface of hot glass or ceramics. The performance of resistors varies greatly depending on the manufacturing conditions. The main feature of this resistor is high temperature resistance, good chemical stability. The resistivity of this kind of resistor is low, and the resistance value of the small power resistor does not exceed 100KΩ, so the application range is limited, but it can be used as a low-resistance part of the complementary metal film resistor . Metal oxide film resistors are mostly gray, miniaturized to green or light pink, and are four- color ring resistors . Allowable error levels ±5%, ±2%.

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