The capacitor is a frequency-dependent, passive electronic component whose capacitive resistance decreases with increasing frequency. In terms of construction, a capacitor consists of two conductive electrodes that are insulated from each other by a dielectric.
Electric fields build up between the two electrodes when a voltage is applied. Due to these fields, charge shifts occur on the electrodes. Charges flowing away from one electrode are compensated for by charge equalization on the other electrode. Depending on the size of the electrodes, the distance between them and the dielectric, the charge equalization takes place faster or slower, which is related to the size of the capacitor or its capacitance (C).
The capacitive reactance (X(C)) of capacitors is inversely proportional to their capacitance and the applied frequency. The most important characteristics of capacitors are capacitance and tolerance, dielectric strength and insulationresistance.
Capacitors with fixed and variable capacitance
In terms of construction, capacitors are divided into those with fixed capacitance and those with variable capacitance. Fixed capacitors are available with the dielectric ceramic, as ceramic capacitors and multilayer ceramic capacitors( MLCC), as well as mica capacitors, tantalum capacitors and niobium capacitors, and Styroflex and film capacitors. Capacitors with large to extremely large capacitances from over 1 µF up to 100,000 µF have a slightly different construction and use a liquid, the electrolyte, as the cathode. Hence the name electrolytic capacitor. Even larger capacities have double layer capac itors(DSK) or super capacitors, a protected designation for this are the super caps from Panasonic, which are available for capacities from a few Farad (F) up to a few thousand Farad. In addition, there are the power capacitors, which are mainly used in power electronics and have a dielectric strength of several kilovolts.
The capacitance value of capacitors
The capacitance value of capacitors is either printed on the capacitor as a combination of numbers and letters or by means of a color code. In addition to capacitors with fixed values, whose capacitance values are specified in the standard values or E series, there are others whose capacitance can be varied. These include the mechanical variable capacitors, trimmers, capacitance diodes and the digitally tunable capacitors, Digitally Tunable Capacitors( DTC).
Designs of capacitors for printed circuit board mounting
In terms of designs for mounting on printed circuit boards, there are capacitors for surface mounting, SMT technology, and for through hole technology( THT). As for SMD designs, these can be" chip technology" and have contact pads at the ends for soldering, or as a V-chip, where the contacts are on the bottom of the capacitor. Cylindrical capacitors for through-hole technology have axial or radial lead wires. Large capacitors may also have a screw cap to make them easier to attach to the chassis or PCB.
Capacitors are used in combination with resistors for charge circuits in multivibrators and flip-flops, as differentiators and integrators, and for analogfilters; in combination with inductors, they are used in resonant circuits and filters.