On Wed, 31 May 2006 07:16:29 +0100, Pooh Bear
>John Larkin wrote:
>> They're serious. They can reduce radiated EMI from switching power
>> supplies and digital electronics, enough to make the difference
>> between passing and failing FCC and CE regs.
>> Ferrite beads can also reduce suceptability by blocking rf entry and
>> nuking cable resonances. I reduced the RF sensitivity of one of my
>> temperature controllers by over 20:1 by passing the thermocouple leads
>> through a figure-8 (dual hole) ferrite bead, apparently by taming a
>> few prominent high-Q resonances.
>Those figure 8s are handy. I used them on a product's intenal ac mains leads
>together with a couple of Y caps to get it inside the conducted limits. It was
>previously just a couple of dB over. A heck of a lot cheaper thana full blown
We use them on switching supply outputs, too. They give both
common-mode and differential loss.