The function of capacitors.

Capacitors have multiple functions in circuits, mainly including the following aspects:

Energy storage: Capacitors can store electric charges and electric field energy. When the power supply voltage is higher than the voltage across the capacitor, the capacitor charges and stores electrical energy; When the power supply voltage is lower than the voltage across the capacitor, the capacitor discharges and releases the stored electrical energy. This energy storage characteristic enables capacitors to act as energy buffers and regulators in circuits, such as in camera flash circuits where capacitors store electrical energy and provide instantaneous high current for the flash.

Filtering: Used to filter out AC components in the power supply, making the output DC voltage smoother. In the power circuit, the rectified voltage contains a certain amount of AC ripple. By connecting a capacitor to the output terminal of the rectification circuit, the capacitor can bypass the AC ripple, allowing the DC component to pass smoothly and obtain a stable DC voltage.

Coupling: Used to connect circuits of different levels, allowing AC signals to pass smoothly while blocking DC components. In audio amplifiers and other circuits, the output signal of the front-end circuit usually contains DC and AC components. By connecting the front-end output to the back-end input through a coupling capacitor, the AC audio signal can be transmitted to the back-end for amplification, while preventing the DC component of the front-end from entering the back-end and avoiding affecting the operating point of the back-end circuit.

Bypass: Bypass high-frequency noise or interference signals in the circuit to ground, thereby reducing their impact on other circuit parts. For example, in digital circuits, rapid signal switching can generate high-frequency noise. Connecting a small capacitor near the power pin of the chip to ground can bypass these high-frequency noises and ensure the stable operation of the chip.

Tuning: In LC resonant circuits, capacitors and inductors work together to select and tune specific frequency signals. In the tuning circuit of a radio, by adjusting the capacitance value of the capacitor, the resonant frequency of the LC resonant circuit can be changed, allowing the radio to receive radio signals of different frequencies.

Voltage division: When multiple capacitors are connected in series, they will share the total voltage in proportion to their respective capacitance values, playing a role in voltage division. In some circuits that require precise voltage control, such as high-voltage measurement circuits or certain sensor circuits, the voltage division characteristics of capacitors are utilized to obtain appropriate voltage signals.