jb Plastic Film Capacitor—Dielectric Types

Film Capacitors are Non polarized, and may be used in AC or DC circuits.
Typical values range form 1000pF to 1uF for Polyerster Film, and 0.01uF to 18uF for Metallized Film capacitors. Standard Film Capacitor values change in multiples of 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82.

Normal Temperature Coefficient [TC] for Film Capacitors is +7%.

  • Mylar: has a wide temperature change of 20% over -55 to +125°C. Moisture absorption is half that of paper.
    Mylar is the same as polyester. The term Mylar is a trade name.
  • Polycarbonate: Out performs Mylar in all areas. Low Power factor, works best with AC. Polycarbonate has a low temperature drift (graph below), dissipation factor, and dielectric absorption. Use polyphenylene sulfide as a possible replacement.
  • Polyester: Replaces paper for many applications, and smaller in size. Polyester does not have the moisture problem that paper does, but does have a worse tolerance, at 20% ~ over -55 to +125°C. May also be called PETE, or PETP. The Polyester Dielectric has an Absorption of around 0.20%.
  • Polypropylene: It has negative temperature coefficient.
  • Polysulfone: Has a very high operating temperature of +170°C.
  • Polystyrene: Will only work to +65°C. It has a flat to negative temperature coefficient.
  • Teflon: Has a very high operating temperature of +170°C.