What is the function of resistance?

Resistors are one of the most fundamental components in electronic circuits, and their core functions can be summarized into the following five points, demonstrating their irreplaceability through different application scenarios:
1. Current controller - precise current limiting
In LED lighting circuits, if 220V mains power is directly connected to LED beads, the instantaneous current will burn out the components. At this point, connecting a resistor of appropriate resistance in series can limit the current to a safe range of milliampere level. This current limiting characteristic is particularly important in battery powered equipment, as it can prevent accidental triggering of the over discharge protection circuit and extend the device's battery life.
2. Voltage regulator - flexible voltage divider
In analog circuit design, when the amplitude of the sensor output signal does not match the input range of the AD converter, precise scaling can be achieved through a resistive voltage divider network. For example, dividing a 5V signal into 1.25V in a 1:4 ratio preserves signal characteristics while adapting to subsequent processing units. This voltage division mechanism is widely used in industrial instrument calibration.
3. Signal Purifier - Efficient Filtering
At the output end of the switching power supply, the RC filtering network composed of resistors and capacitors can effectively suppress ripple. When the switching frequency is 100kHz, selecting an appropriate RC time constant (usually 1/10 of the switching period) can reduce the output voltage fluctuation from 5% to below 0.5%, ensuring that the digital chip obtains pure power.
4. Energy Converter - Controllable Heating
The resistance wire in the electric blanket converts electrical energy into thermal energy through Joule effect, and its resistance design needs to balance heating efficiency and safety. For example, when using 220V/50Hz power supply, selecting a 48.4 Ω resistance wire can achieve a heating power of 500W, which can be combined with a temperature control switch to form a complete temperature regulation system.
5. Impedance Coordinator - Matching Optimization
In RF circuits, 50 Ω characteristic impedance matching is crucial. By using a π - type resistor network (two series resistors plus one parallel resistor), the impedance of a 100 Ω transmission line can be converted to 50 Ω, reducing the signal reflection coefficient from 0.33 to 0.04 and significantly improving the quality of high-frequency signal transmission. This plays a key role in the construction of 5G base stations.
Modern electronic systems have higher requirements for resistance performance: the error range of precision resistors has reached 0.01%, the self resonant frequency of high-frequency resistors has exceeded GHz level, and the power density of thin film resistors has reached 5W/mm ². These technological breakthroughs have enabled resistors to continue to play a fundamental supporting role in cutting-edge fields such as quantum computing and new energy vehicles, confirming their position as the cornerstone of circuits.