Ferrite coil

To keep the internal ohmic resistance in a coil low, it is necessary to use very thick wire, which makes the coil both large and expensive. For this reason, ferrite is used for the coil core because it increases inductance considerably for the same number of windings. The drawback of this solution is that increasing inductance will only work up to a certain current level. At this point, the ferrite shows signs of saturation and the coil begins to produce heavy distortion.