Types of Capacitors

Imagine there is a pipe, with water flowing through it. Consider both ends of the pipe are blocked. The water pipe now becomes a storage. Similarly, a capacitor consists of two parallel conductive plates, each hosting an opposite electric charge.

The plates are separated by a dielectric or an insulation, which helps in storing the electric charge created between the plates. Capacitors are often storage depots for analog signals and digital data.

They are used extensively in electronic circuits with the purpose of blocking direct current (DC), thereby allowing alternate current (AC) in filter networks and outputs of power supplies.

These are the most popularly used capacitors, which have a wide tolerance capacity ((-)50% - (+)100%). This type consists of two plates (made of aluminum or tantalum), which are wound around each other. The dielectric filled between these plates is mostly a thin layer of oxide (less than 10 microns).

The two popular kinds available in the market are aluminum and tantalum. These are polarized and hence proper care must be taken when fixing them in electronic circuits. If connected incorrectly, they may get damaged.

Usage: They have a large capacitance value. Hence, they are widely used as coupling capacitors in audio applications and in smoothing applications for power supplies to reduce ripple voltages.

These are the simplest form of capacitors, which contain a set of moving plates. These plates mesh with another set of fixed plates. The position of the moving plates with respect to that of the fixed plates determines the capacitance generated.

Usage: They are widely used in tuning transmitters and receivers. They are also used in transistor radios.

Film capacitors have a capacitance value of 5 pF - 100 pF (pico farad). The basic difference between these and the other types is in their dielectric property. There are two kinds available - radial lead type and axial lead type.

The former one has metal film electrodes containing a dielectric layer between them, whereas the latter one has metal sheets wrapped around the electrode with dielectric material sandwiched within the sheets. The most common kind available in market are Mylar, polystyrene, polypropylene, and Teflon capacitors.

Usage: They are mainly used in devising circuits for harmonic filtering and reactive energy compensation.

These are also known as disc capacitors. They are made by coating the sides of a ceramic disk with silver. One can make both low capacitance and high capacitance in this type, by changing the thickness of the ceramic disc used. For low capacitance values, a ceramic disc (3 - 6 mm ) can be used.

They usually have a high dielectric constant and show non-linear changes in capacitance value when exposed to high temperatures, as they are non-polarized devices. Their voltage ratings are usually low and capacitance value ranges between a few picofarads to 1 micro farad.

Usage: They are used as bypass capacitors in decoupling circuits.

These types are used in almost all industrial applications based on electromagnetism, be it coupling and decoupling circuits or smoothing the power supplies. Capacitors are like storage wells of energy, where the stored energy is called voltage.

Even the door bell of your home has this component. This is how this tiny component serves a big purpose in this electronically run world today.