What are mica capacitors for?
Common mica and silver mica capacitors are used in precision circuits and high frequency circuits. The characteristics of mica as dielectric makes this material ideal for the elaboration of precision capacitors and still able to operate at very high frequencies. Thus, we find these capacitors in RF instruments, transmitters, and many other circuits that operate with high frequencies. In the figure a capacitor of this type. Older types have a special reading code in which the colored specks give the value. Because of their characteristics these capacitors are found in the range of low values (up to a few hundred picofarads).
