Capacitors are very common components in electronic circuits and are second only to resistors as a circuit element in electronics and a large assortment is usually found in every electronics workshop. They are used in filters, both in power-supply filters and in signal filters, often in connection with operational amplifiers.
Capacitors are important in integrated circuits, and may be made from metal or poly silicon films with silicon dioxide dielectrics on silicon. They are used in several different ways in electronic circuits including sometimes to store a charge for high-speed use.
They are very common elements and are one of the three basic electronic elements along with resistors and inductors that make up all passive electrical circuits. Generally they are cylindrically shaped and have 3/8 brass studs for connections to flat bar or other heavy conductors, and can be found in many electrical and electronic devices such as the flash in a camera. Ceramic capacitors are another old favorite, relying on the very high dielectric constants of ferroelectric ceramics. Unfortunately, ceramic capacitors are not very stable and have high losses, though this is not serious in their usual applications.
Capacitors are designed to withstand a certain maximum voltage and are close to ideal if the voltage does not vary too rapidly, and is not excessive. Electrolytic capacitors are probably the most sensitive to temperature extremes. The oxide layer grows with one polarity, but is dissolved with the other polarity, so electrolytic capacitors are polarized, and must be connected the right way round in a circuit.
For large capacitances, the thin, chemically-deposited dielectric layers of the electrolytic capacitors are the choice.
At the present time, air-dielectric tuning capacitors are not common, having been replaced by smaller capacitors with mica or plastic dielectrics.
Filter capacitors are common in electrical and electronic work, and cover a great number of applications.
Experts say that if capacitors are not made right, they start to deteriorate after three or four years, rather than lasting the expected seven years.
admin