The classification and characteristics of various capacitors

1. Aluminum electrolytic capacitor

It is made of aluminum cylinder negative electrode, which is filled with liquid electrolyte, inserted into a curved aluminum strip made of positive electrode. The DC voltage treatment is also required to form a layer of oxide film on the positive electrode as a medium. Its characteristics are large capacity, but large leakage, poor stability, positive and negative polarity, suitable for power supply filtering or low-frequency circuit, when used, positive and negative poles should not be reversed.

2. Tantalum electrolytic capacitors

It uses a metal tantalum or niobium as a positive electrode, and a diluted solution such as dilute sulfuric acid as a negative electrode and is made of a dielectric film formed on the surface of a tantalum or niobium. Its characteristics are: small size, large capacity, stable performance, long life. High insulation resistance. Good temperature performance for use in demanding equipment.

3. Ceramic capacitor

With ceramic media. A silver layer is sprayed on both sides of the ceramic substrate and then fired into a silver film as a polar plate. Its characteristics are: small size, good heat resistance, low loss, high insulation resistance, but small capacity, suitable for high-frequency circuits. Ferroelectric ceramic capacitors have a large capacity, but have a large loss and temperature coefficient and are suitable for low-frequency circuits.

4. Mica capacitors

The electrode plate is made by spraying silver layer on the metal foil or on the mica plate, the electrode plate and the mica layer are stacked one on another, and then die-casted in bakelite powder or sealed in epoxy resin. Its characteristics are: small dielectric loss, high insulation resistance. Low temperature coefficient, suitable for high frequency circuits.

5. Film capacitor

The structure is the same as the paper capacitor, the medium is polyester or polystyrene. Polyester film capacitors, high dielectric constant, small size, large capacity, good stability, suitable for bypass capacitors. Polystyrene film capacitors have small dielectric loss and high insulation resistance, but they have a large temperature coefficient and can be used in high-frequency circuits.

6. Paper capacitors

Two sheets of metal foil are used as electrodes, sandwiched between extremely thin capacitive paper, rolled into cylindrical or flat cylindrical cores, and then sealed in a metal shell or insulating material shell. It is characterized by its small size and large capacity. However, the inherent inductance and losses are relatively large and are suitable for low-frequency circuits.

7. Metallized paper capacitors

The structure is basically the same as the paper-membrane capacitor. It is coated with a metal film on the capacitor paper to replace the metal foil. It has a small size and a large capacity and is generally used in low-frequency circuits.

8. Oil-immersed paper capacitor

It is a paper dielectric capacitor immersed in specially treated oil, can enhance its withstand voltage. Its characteristics are large capacity, high pressure, but the larger size. In addition, in practical applications, the first to choose different types of capacitors based on different uses; the second to consider the nominal capacity of the capacitor, allowable errors, pressure values, leakage resistance and other technical parameters; the third for positive, For negative electrode electrolytic capacitors, positive and negative electrodes must not be reversed during welding.