The role and principle of capacitors

Capacitors are almost indispensable energy storage elements in electronic circuits. They have the characteristics of blocking DC, communicating with AC, and blocking low frequencies. Widely used in coupling, blocking, bypass, filtering, tuning, energy conversion and automatic control circuits.

1. Filter capacitor: Connected between the positive and negative poles of the DC Power Supply to filter unwanted AC components in the DC power supply so that the DC power becomes smooth. Large-capacity electrolytic capacitors or tantalum capacitors are generally used, and other types of small-capacity capacitors can also be connected in the circuit at the same time to filter out high-frequency alternating current.

2. Bypass capacitor: In the circuit of AC and DC signals, connect the capacitor to the two ends of the resistor or a certain point of the circuit and connect it to the common potential. Set a path for AC signal or pulse signal to avoid AC signal. The composition is reduced by the voltage drop across the resistor.

3. Decoupling capacitor: It is connected between the positive and negative poles of the power supply of the amplifying circuit to prevent the parasitic oscillation caused by the positive feedback formed by the internal resistance of the power supply.

4. Coupling capacitance: Connected to the AC signal processing circuit, used to connect the signal source and signal processing circuit or for the inter-stage connection of the two amplifiers to cut off the direct current and allow the AC signal or pulse signal to pass through, so that the front and rear amplifier circuits DC operating points do not affect each other.

5, pad capacitance and resonant capacitance: the auxiliary capacitor in series with the main capacitor, adjust it can make the oscillation signal frequency range becomes smaller, can notably improve the low frequency end of the oscillation frequency.

6. Tuning capacitance: It is connected to the two ends of the oscillation coil of the resonant circuit and plays the role of selecting the oscillation frequency.