A capacitor is an electronic device used in circuits to block DC signals, while still allowing AC signals to pass though them. In order to accomplish this, a ceramic disk capacitor uses a series of alternating metal disks, called plates, and ceramic disks, called dielectrics. They are inexpensive and versatile, and have been in wide use in various types of electronic equipment since the early 1930s.
Capacitors operate through the creation of an electromagnetic field between two or more metal plates, which are insulated from one another by one or more dielectrics. Plates in capacitors are usually made of metals, such as aluminum or tantalum; however, there are many different materials used as dielectrics. Regardless of the plate material, the majority of a capacitor’s operational characteristics are set by its dielectric’s composition.
Dielectrics can electrically insulate a capacitor’s plates from one another, but at the same time, will allow an electromagnetic field to pass though them. When a capacitor is operating, an electrical current enters the capacitor but cannot pass directly to the other plates because they are separated by the insulating dielectric. This prevents an electrical current from passing directly through the capacitor, which blocks any DC signal. An AC signal will create a polarized electromagnetic field around the plate, however. The electromagnetic field will then pass through the dielectrics and induce an AC signal on the other plates in the capacitor, which will then pass out to the rest of the circuit.
As the name suggests, a ceramic disk capacitor uses small ceramic disks as its dielectrics. These disks have several advantages over dielectrics made of other materials such as plastics or oils. Ceramics are very inexpensive, easy to produce, are capable of withstanding relatively high temperatures, and are electrostatically stable. As a result, ceramic disk capacitors find use in electronic devices that generate a lot of heat, operate at very high frequencies, or both.
The ceramic disk capacitor was the first such device created for use in practical electronic applications and equipment. In their early days, these devices worked alongside vacuum tubes. Later, they helped the transistor make its debut. They came to stand shoulder to shoulder with the most advanced field-effect components. From old tube radios, to televisions, to satellites and the most modern supercomputers, there has never been a time in the history of electronics when the humble ceramic disk capacitor did not provide exceptional performance at a very modest cost.