A fixed-value parallel-plate capacitor, integrated or discrete, is one of the most common components in electronics. In the planar technology, the insulator layer can be made conveniently from thermally grown oxide or deposited dielectrics such as silicon nitride or oxide. The plates can be metal, silicide, polycrystalline semiconductor, or the substrate semiconductor that is heavily doped.
The applications of a generic capacitor are listed below:
It is commonly used in filters and tuned circuits.
Energy storage: Energy can be stored for pulsed operations such as spark plugs and pulsed lasers.
Regulation: The basic property of a capacitor is continuity of voltage and charge. A step voltage, for example, is not possible across a capacitor. This property is used to regulate DC voltage nodes and power supplies.
As a speed-up capacitor: It is used to improve the tum-on and turn-off times of a bipolar transistor when connected in parallel to the base resistor.
As an integrator: Examples of applications are analog computing and waveform generation.
As sensors: Since capacitance is proportional directly to the dielectric constant and inversely to the distance, it is used to detect the presence of any material. Examples are level sensor, position sensor, tactile switch, and humidity sensor. Capacitance is also used in a pressure sensor to detect displacement of a diaphragm under differential pressure.
