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Inductors, when applied as inline power filters, need a parallel snubbing diode so that when the load opens, the current can be safely discharged.

In certain contexts, ferrite beads such as the Laird 28L0138 series can be used as inline power filters. These have nonlinear, mixed inductive/resistive properties dependent on frequency.

Since there is some inductance in ferrite beads, should they too have a snubber, or is their internal resistance adequate to discharge current after an opened load?

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  • \$\begingroup\$ They're not really used on circuits that can suddenly go high-impedance, so I'd say that snubbers are not required. \$\endgroup\$ – Ignacio Vazquez-Abrams Jul 11 '18 at 18:08
  • \$\begingroup\$ @IgnacioVazquez-Abrams Would they not be used at the input to a DC power line that could be turned off? \$\endgroup\$ – Reinderien Jul 11 '18 at 18:22
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    \$\begingroup\$ A good ferrite bead is highly lossy rather than purely inductive, so there shouldn't be much stored energy in it even if its current is shut off abruptly. \$\endgroup\$ – The Photon Jul 11 '18 at 18:38
  • \$\begingroup\$ No snubbing needed. analog.com/media/en/analog-dialogue/volume-50/number-1/articles/… \$\endgroup\$ – Sunnyskyguy EE75 Jul 11 '18 at 19:29
  • \$\begingroup\$ @TonyEErocketscientist I really like that paper, but doesn't it reveal that a ferrite bead has an often overlooked MHz-freq parasitic inductance? I would deduce from that unless the snubbed frequency is out of this range, a snubber would help where it could also help with an inductor. \$\endgroup\$ – mehmet.ali.anil Jul 11 '18 at 21:21
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Since there is some inductance in ferrite beads, should they too have a snubber, or is their internal resistance adequate to discharge current after an opened load?

Short answer, No. Why? because ferrite is a magnetic material with a saturation point (whereas coils with air do not saturate magnetically). Ferrite material also has more magnetic resistance and is lossy. So you will store less energy. The internal resistance will help dampen out sharp rises associated with "instantaneous" changes in current.

There will however, be some ringing at high frequencies (as shown in figure B below) when used with a capacitor in a filter, and there are better ways to compensate the circuit (Method C) to avoid overshoot.

enter image description here
Source: http://www.analog.com/en/analog-dialogue/articles/ferrite-beads-demystified.html

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