Capacitor Types and Uses - Tutorial
Capacitor Types and Uses
The capacitors are classified based on the material used for the dielectric.
- The major types of capacitors are
(1) Variable Air Capacitor,
(2) Mica Capacitor,
(3) Paper Capacitor,
(4) Ceramic Capacitor,
(5) Plastic Capacitor &
(6) Electrolytic Capacitors.
- The choice of capacitor type for the particular application depends upon number of factors like
(1) the working voltage,
(2) the capacitance value,
(3) the stability,
(4) the tolerance,
(5) the leakage resistance,
(6) the price &
(7) the size.
In this post, let us understand various types of capacitors, their advantages, applications in detail. Before proceeding further it is recommended to know about How Capacitor Works?
- It is the simplest form of capacitor.
- It consists of two strips of aluminium foil separated by sheets of waxed paper. This whole setup is rolled up into the form of a cylinder.
- Metal end caps is used to make the electrical connections to the foils. Then the whole assembly is encapsulated in a case.
- By rolling up the foil and paper a comparatively large cross-sectional area can be produced with reasonably compact dimensions.
- Variation in capacitance with temperature change.
- Shorter life time than most other types of capacitor.
- It is the most common form of variable capacitor.
- One set of plates is fixed, whereas the other set will be rotated to give either more or less overlap between the two.
- This makes variation of the effective cross-sectional area which leads to variation of capacitance.
- This type of capacitors are used in radio and electronic circuits where very low losses or variable capacitance are required.
- This is the type of device connected to the station tuning control of a radio.
- In this type of capacitors, the whole capacitor is impregnated with wax and placed in a bakelite case.
- Mica can be easily obtained in thin sheets and it is a good insulator.
- But mica is expensive and is not used in capacitors above about 0.2 μF. A modified form of mica capacitor is known as silvered mica type.
- Here the mica is coated on both sides with a thin layer of silver which forms the plates.
- In this type the capacitance value is stable with less tolerance.
- No ageing factor( capacitance value will not decrease with the age).
- Their capacitance value will be constant with change of temperature.
- They have high voltage rating, service life.
- They are used in high frequency circuits with fixed values of capacitance up to 1000 pF.
- But they are costlier than some other types.
- In this case, the dielectric may be of polystyrene, polyester, polypropylene or polycarbonate.
- Each material has different electrical characteristics.
- The construction of plastic capacitors are similar to paper capacitors. Their different characteristics are listed in Table.
- Their construction depends upon the value of capacitance required.
- For high values, a tube of ceramic material is used as shown in the figure.
- For smaller values the cup construction or the disc construction is used.
- As some ceramic materials have high permittivity, high capacitance with a high working voltage rating in a small physical size can be achieved.
- These capacitors are available from 1 pF to 0.1 μF.
- They are used in high frequency electronic circuits in a wide temperature range .
- In contrast to other type of capacitors, the electrolytic type capacitors have the polarities (Polarized capacitor).
- They should connect to the circuit with correct polarity.
- If it is not connected with proper polarity the capacitor will be destroyed since the oxide layer will be destroyed.
- They have the highest value of capacitance and working voltages.
- The electrolytic capacitors have wide tolerance value ( values are not accurate)
- Their construction is similar to the paper capacitor. But aluminium foil used for the plates instead of paper.
- A thick absorbent material like a paper impregnated with an electrolyte (ammonium borate) is used to separate the plates.
- The assembled capacitor is packed in an aluminium container and hermetically sealed.
- The dielectric material consists of either an aluminium oxide or tantalum oxide film.
Comparison of Various Types of Capacitors
|Paper||1nF–40μF||Cheap. Poor stability|
|Air||5pF –1nF||Variable. Good stability|
|Polycarbonate||100pF –10μF||Low loss. High temperature|
|Polyester||1nF –2μF||Cheap. Low frequency|
|Polypropylene||100pF –10nF||Low loss. High frequency|
|Polystyrene||10pF–10nF||Low loss. High frequency|
|Silvered mica||10pF–10nF||High stability. Low loss|
|Ceramic||2pF 100nF||Low temp coefficient. High
|Electrolytic||1–100 000μF||High loss. High leakage|
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