Film capacitors are passive electrical components that use an extremely thin plastic film as their dielectric. Also called polymer film capacitors, film dielectric capacitors, and plastic film capacitors, these components are as common as electrolytic capacitors and ceramic capacitors. They are intended for electronic circuits, AC/DC microelectronics, and electronic equipment.
These electrical capacitors are wrapped around a cylindrical-shaped winding and have two metallic electrodes-covered plastic films. Since film capacitors are non-polarized, the attached terminals can be interchanged.
Film capacitors are called plastic capacitors (or metalized capacitors) because they are often metalized. Polyphenylene Sulfide or PPS, Polyethylene terephthalate or PET, Polypropylene or PP, and PTFE or Polytetrafluoroethylene are the dielectrics that are popularly utilized for film capacitors.
These electrical components have features that make it different from other capacitors. They are versatile, equipped with excellent frequency characteristics, and have extremely low distortion factor. Film capacitors are also durable; they do not easily submit to wear and tear, which makes them ideal for decoupling/coupling circuits, audio circuits, ADC, and other high frequency and high voltage applications.
There are several types of film capacitors, like Polypropylene and Polyester Capacitors, which are based on the dielectric materials utilized in the film capacitor.
- Polypropylene Capacitors are film capacitor types where the dielectric material is created out of polypropylene, a kind of polymer. There are approximately 10 film capacitors that have polymer as their dielectric.
- Polyester Capacitors are made of polyethylene terephthalate polymer. It is sometimes referred to as PET Film Capacitors or Polyester Film Capacitors.
Aside from the above-mentioned, there are other types of film capacitors, like Metalized Film Capacitors and Film/Foil Capacitors, which are categorized according to construction.
- Metalized Film Capacitors have compact shapes and sizes, self-healing characteristics, and are used in switching circuits, DC link circuits, and pulse circuits.
- Film/Foil Capacitors have two aluminum foil electrode layers. They can be non-inductive or inductive, and are used for bypassing, decoupling, coupling, and high frequency-switching circuits like power supplies and oscillator circuits.