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Currently learning about ferrite beads.

I have noticed that on the data sheets they have graphs of impeadance vs frequency.

to ensure you have the best ferrite for the job I assume you want to get the greatest impeadance at the frequency you are experiencing the noise.

Can anyone confirm why having a greater impeadance is better?

Thanks SS

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    \$\begingroup\$ Do you understand what impedance is and can tell it in your own words? \$\endgroup\$
    – PlasmaHH
    Commented Oct 29, 2015 at 11:14
  • \$\begingroup\$ Yes, I can confirm that having a greater impedance at noise frequency is better. Impedance is like a barrier preventing noise from entering your system: the higher it is, the better. \$\endgroup\$
    – Dmitry Grigoryev
    Commented Oct 29, 2015 at 11:55

1 Answer 1

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In this context, you can (sort of) think of a ferrite bead as being a frequency-variable resistor. The higher the frequency, the higher the resistance.

A resistor by itself doesn't attenuate anything, but does with a load following it. Something will be on the output side of the ferrite bead, and this something will have some input impedance. The ferrite bead impedance and this input impedance together form a voltage divider. Note that the higher the ferrite bead impedance, the more the signal is attenuated.

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