A capacitor is an electronic component that holds and releases electrical charges. The basic principle of a capacitor is to charge and discharge, and of course to rectify, oscillate, and other functions. In addition, the structure of the capacitor is very simple, mainly composed of two positive and negative electrodes and the insulating medium sandwiched in the middle, so the type of capacitor is mainly determined by the electrode and the insulating medium. Capacitors have many uses, mainly as follows:

1. Dc isolation: The function is to prevent the passage of DC and allow AC to pass.

2. Bypass (decoupling) : Provides a low impedance path for certain parallel components in an AC circuit.

3. Coupling: A connection between two circuits that allows AC signals to pass through and be transmitted to the next level of electricity

4. Filtering: This is very important for DIY. The capacitors on the graphics cards are basically used for this purpose.

5. Temperature compensation: for the influence of other components on the temperature adaptability is not enough, and compensation, improve the stability of the circuit.

6. Timing: A capacitor is used in conjunction with a resistor to determine the time constant of a circuit.

7. Tuning: Systematic tuning of frequency-dependent circuits, such as cell phones, radios, and television sets.

8. Rectifying: Turning on or off the semi-closed conductor switch element at a predetermined time.

9. Energy storage: To store electrical energy for release when it is needed. Such as camera flash, heating equipment, etc. (Some capacitors are now close to the level of lithium-ion batteries, storing enough energy to power a mobile phone for a day.