ferrite bead
As can be seen from the name ferrite bead, it is a smaller bead-shaped component made of ferrite. Ferrite is a mixture of iron oxide, nickel, zinc or manganese oxides with a crystalline structure. It is magnetically conductive and has soft magnetic or hard magnetic properties with lower or higher permeability depending on the mixture.
Ferrite beads are bead- or cylinder-shaped and have one or more holes in the center through which a current-carrying conductor is passed. For the current flowing through it, a ferrite bead forms a combination of inductance and resistance and thus a low-pass filter with pronounced damping behavior.
Ferrite beads are used to suppress RF interference radiation and to decouple low- voltage power supplies from irradiation. For this purpose, they are placed over the lines carrying the supply voltages. In accordance with the low-pass behavior, ferrite beads form no or low resistance for DC voltage and low- frequency voltages, but for high frequency the frequency resistance increases rapidly.
In memory technology, there used to be the concept of core memory. These were ferrite beads with a strongly pronounced rectangular hysteresis, whose remanence served to store the two logical states.