You may have heard lots about ferrite beads, but you may be wondering – how do ferrite beads work? Unfortunately, they are not the most straightforward to understand. If you need to use them, then you need to understand them thoroughly. For example, you must understand their electromagnetic characteristics as they can change while being used. Once you are knowledgeable about ferrite beads, one must be selected for the circuit board. If you don’t select the correct one, it will cause problems.

How do ferrite beads work?

Electronic components use ferrite beads to attenuate high frequency signals. You may think that they are inductors, but ferrite beads are more complex than inductors.

A ferrite bead can be modeled as capacitors and inductors, and resistor all in parallel, with a series resistor in front of them. The series resistor represents resistance to DC currents. The inductor is the primary component for attenuating high-frequency signals. The parallel resistor signifies AC current losses. The capacitor shows a parasitic capacitance. When looking at the impedance vs. frequency curve of a ferrite bead you can see that the impedance, which is mostly resistive, is extremely high in only a thin band. That section is where the inductance of the bead dominates. Above that band, the parasitic capacitance takes over and rapidly reduces high-frequency impedance.

Beads are usually rated for a certain DC current. Amperages above the specified value can damage the component. The troublesome thing is that this limit is drastically affected by heat. As temperature increases the rated current quickly decreases. Rated current also affects the ferrite’s impedance. As DC current increases, a ferrite bead will “saturate” and lose inductance. At relatively high currents, saturation can reduce impedance by up to 90%.

Where To Buy?

Click here to see our ferrite components. Express Transformers and Controls Ltd are a trustworthy transformer manufacturer that offers you quality products with support at the price you can afford. Reap the benefits of quality transformers from us today!


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Please feel free to contact us to discuss your design requirements. Our lead engineer details are listed below and they are very happy to discuss your particular project needs with you.