What is a Ferrite Bead?
Ferrite beads or chip inductor beads are passive electronic components that can suppress high frequency signals on a power supply line. They are normally placed around a power/ground line pair that is incoming to a particular device, such as the power cord for your laptop. These beads work according to Faraday’s Law: the magnetic core around a conductor induces a back EMF in the presence of a high frequency signal, essentially attenuating the ferrite frequency response.
Ferrites are magnetic materials, and placing this material in a ferrite clamp around the power supply/ground line provides a source of inductive impedance for signals passing through the line.
Ferrite bead model
A ferrite bead can be modelled as capacitors and inductors, plus a resistor in parallel with this RLC network wired with a series resistor. The series resistor quantifies the device’s resistance to DC currents. The inductor in this model represents a ferrite beads primary function of attenuating high-frequency signals, i.e., providing inductive impedance through Faraday’s Law. The parallel resistor in this model accounts for losses in eddy currents that are induced within the ferrite bead at high frequencies. Finally, the capacitor in this model accounts for the component’s natural parasitic capacitance.
Fair-Rite, for example, offers a broad selection of cost-effective multi-layer chip inductor beads to suppress conducted EMI signals. Chip inductor beads can be used in an array of devices such as cellular phones, computers, laptops, pagers, etc. The small package sizes accommodate automated placements and allow for a dense packaging of circuit boards.
Chip Inductor Beads are available in standard, high and GHz signal speeds.
