Re: gEDA-user: bypass caps

[ldoolitt@xxxxxxxxxxxxxxx]

DJ -

On Mon, Aug 21, 2006 at 12:56:37AM -0400, DJ Delorie wrote:
> 
> 0.1 uF or 1 uF ?  Same footprint (0603), the 1uFs are a few cents more
> each (er, ~ 40% more cost for 10x the capacitance).
> Don't know if the 0.1uFs have some benefits inductance-wise or
> ESR-wise, in general.

This is indeed the trick -- it's unusual to get believable
parasitic inductance information from capacitor manufacturers.
ESR on a ceramic cap is pretty close to zero; all the damping
at the LC resonance will come from the parallel resistance
provided by your circuit.

I found some nice ceramic capacitor inductance curves
(representative, not definitive) from AVX.  Go to Digi-Key,
bring up a page of 0.1 uF ceramic capacitors, and click
through to the datasheets.  Like I say, some manufacturers
are more helpful than others.  The actual parts probably
don't change much, as long as you stick to the same package
size and dielectric type.

   - Larry


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