The Basics of Capacitors

A capacitor is composed of two metal electrodes sandwiching an insulator (also called a dielectric). When a voltage is applied between two electrodes, charge is stored on the electrodes. So capacitors are actually components that store electrical energy. Capacitors are represented by "C".


1. Fixed capacitor

The capacitor cannot be changed, it is fixed and cannot be adjusted.

2. Variable capacitor

The capacity of variable capacitors can be continuously changed within a certain range, often divided into "single" and "double". They have several metal sheets of the same shape and are connected into a set of fixed pieces and a set of moving pieces.

3. Semi-Variable Capacitor

Also known as trimmer capacitor or compensation capacitor. Capacitor capacity can be changed in a small range, and its variable capacity is several to tens of picofarads, up to 100pF. It is suitable for occasions where the capacitor does not need to be changed frequently after collection and adjustment, and air, mica and ceramics are often used as the medium.

To identify the performance of a capacitor, it can be measured by the main parameters such as nominal capacitor, capacitance tolerance, withstand voltage (or rated DC working voltage), and insulation resistance.

Capacitor allowable error:

The actual capacitor often has a certain deviation from the nominal capacitance, which is called capacitor error (or deviation). The allowable maximum deviation range of the actual capacitor for the nominal capacitor is called the capacitance allowable error.

Capacitor withstand voltage: The withstand voltage refers to the maximum DC working voltage that the capacitor can withstand. Under this voltage, the capacitor can work for a long time without being broken down, so the withstand voltage is also called the rated DC working voltage, and its unit is volts (V).