Re: tiny inductor with every bypass cap?

On Sat, 21 Jun 2008 15:25:38 -0700 (PDT), bill.sloman@[EMAIL PROTECTED]
 wrote:

>On Jun 22, 5:52 am, Paul Keinanen <keina...@[EMAIL PROTECTED]
> wrote:

>> Are you sure that these are ordinary inductors or just a wire through
>> a ferrite bead?
>>
>> While the ferrite will increase the inductance, a suitable ferrite
>> material is also quite lossy at higher frequencies, reducing the risk
>> for unwanted resonances with the capacitors.
>
>Sadly, you can't rely on this. I've had to put little resistors in
>series with ferrite bead to kill a resonance - admittedly at a few
>hundred kHz, where the bead doesn't look that lossy.

It would be quite hard to find material that would be lossy at such
low frequencies. For instance materials listed at
http://www.fair-rite.com/newfair/materials.htm
start at 1 MHz
(material 31), while the common material 73 have significant losses
only above 10 MHz.

Paul