The capacitor has the following characteristics, that is, it can be charged and discharged instantaneously. Direct current will not pass, but exchanges will pass; the higher the frequency, the easier the communication will pass. The application of these characteristics in the circuit.

Typical circuit usage method.

1. Electrical discharge circuit

The discharge circuit is a circuit that makes the additional load work by releasing the charge stored in the capacitor. Since the discharge circuit can be used as a camera flash or as a backup power source in an emergency, it can release a large current in the flash memory. In the circuit example, if the switch is connected to the power supply side, the capacitor will be charged. When the charge accumulates to the power supply voltage, it stops. If the switch is connected to the load side, the capacitor starts to discharge and the light bulb starts to light up.

2. Filter circuit

A smoothing circuit is a circuit that converts the alternating current into a direct current after rectifying it. Power lines are a typical example. In the diode bridge circuit, the voltage wave thrust pulse obtained by the rectified input voltage is flattened by the capacitor.

3. Decoupling circuit

The decoupling circuit, as the name suggests, uses a capacitor circuit to separate the signal coupling. In this example, as shown in the figure, by adding a capacitor to the channel line containing high-frequency AC components in the basic DC, only the high-frequency components are separated by the capacitor, and then noise is not transmitted. Eliminating the switching noise in the switching power supply is such a purpose.

4. Coupling circuit

A coupling circuit is a circuit that does not allow DC components to pass, but only allows AC components to pass. The coupling circuit is used when it is affected by the DC component, which is also called DC cut, etc. It is not included in the amplifying circuit of the audio signal.

In addition, there are various applications such as resonance, filter, standby, time constant, and power factor improvement circuits.