Classification and characteristics of various capacitors (II)

5. Film capacitors:

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

6. Paper capacitor:

Two pieces of metal foil are used as electrodes, sandwiched in extremely thin capacitor paper, rolled into a cylindrical or flat cylindrical core, and then sealed in a metal shell or an insulating material shell. It is characterized by a small size and a large capacity. However, the inherent inductance and loss are relatively large, which is suitable for low frequency circuits.

7. Metallized paper capacitors:

The structure is basically the same as that of the paper capacitor. It is coated with a metal film on the capacitor paper to replace the metal foil. It is small in size and large in capacitance, and is generally used in low frequency circuits.

8. Oil-impregnated paper capacitors:

It immerses the paper capacitor in a specially treated oil to enhance its withstand voltage. It is characterized by large capacitance and high withstand voltage, but it is bulky. In addition, in practical applications, the first is to choose different types of capacitors according to different purposes; the second is to take into account the nominal capacity of the capacitor, the allowable error, withstand voltage, leakage resistance and other technical parameters; For a negative electrolytic capacitor, the positive and negative electrodes should not be reversed during soldering.