Types Of Capacitors

 

Types Of Capacitors

There are four types of capacitors in Electronics

1. Mica Capacitors
2. Ceramic Capacitors
3. Paper Capacitors
4. Electrolytic Capacitors
5. Variable Capacitors

1. Mica Capacitors

Mica Capacitors are constructed from plates of aluminum foil separated by sheets of mica. The plates are connected to two electrodes. The mica capacitors have excellent characteristics under stress of temperature variations and high voltage applications. Mica capacitors are available from capacitance range from 5 to 10000pf (PICO farad). Mica capacitors are usually rated at 500v. Its leakage current is very small is about 1000Mega ohm.

2.Ceramic Capacitors

Ceramic Capacitors are made in many shapes and sizes. However, the basic construction is the same for each. A ceramic disc is coated on two sides with a metal, such as copper or silver. These coatings act as the two plates. During the manufacture of the capacitor, tinned wire leads are also attached to each plate. Then the entire unit is coated with plastic and marked with its capacitance value. Besides the value of the capacitor, its also indicates the tolerance and temperature coefficients.

Ceramic Capacitors are very versatile. Their working voltage ranges from 3v up to 6000v. The capacitance ranges from 3pf(pico farad) to about 2uf(micro farad).Ceramic capacitors have a very low leakage currents about 1000(Mega ohm) and can be used in both AC and DC circuits.

3. Paper Capacitors

The basic construction of Paper capacitor is very simple. In a paper capacitor paper is rolled in between two metal foil, it is possible to concentrate a large plate area in a small volume. The capacitor consists of two metal foils separated by strips of paper. This paper is impregnated with a dielectric material such as wax, plastic or oil.

Paper capacitors have capacitance ranging from 0.0005uf(micro farad) to several uf (micro farad), and are rated from about 100v to several thousand volts. They can be used in both AC and DC Circuits.

4. Electrolyte Capacitors

Electrolyte capacitors are extremely varied in their characteristics. The capacitance value may range from 1uf (Micro farad) to several thousand micro farads. The voltage ratings may range from 1v to 500v, or more. These capacitors are commonly used in situations where a large capacitance is required.

The electrolyte capacitor consists of an aluminum foil electrode which has an aluminum-oxide film covering on one side. The aluminum plate serves as the positive plates and the oxide as the dielectric. The oxide is contact with a paper with an electrolyte. The electrolyte forms the second plate(negative) of the capacitor. Another layer of aluminum without the oxide coating is also provided for making electrical contact between one of the terminals and the electrolyte.

In most cases the negative plate is directly connected to the container of the capacitor. Therefore, container act as the negative terminal of the capacitor. These capacitors are used mostly in DC circuits

5. Variable Capacitors

In some circuits, such as tuning circuits, it is desirable to be able to change the value of capacitance readily. This is done by means of a variable capacitor.