Re: gEDA-user: Eliminate separate Vcc planes?

[Darrell Harmon <dlharmon@xxxxxxxxxxxx>]

On Tue, Oct 20, 2009 at 4:38 AM, Gabriel Paubert <paubert@xxxxxxx> wrote:
>> I have done some testing of various passives (mostly 0402) and came to
>> the conclusion. I tested both shunt and series capacitors on a 50 ohm
>> transmission line with a VNA. What was most interesting to me was that
>> the large value capacitors performed better as series coupling caps
>> than the small ones. The single layer caps in the 1 to 100 pF range
>> frequently had parallel resonances in the 10 to 30 GHz range. Most of
>> the multilayer caps (10 nF to 1 uF) performed well to at least 30 GHz.
>
> And for the shunt case?
>
> Some manufacturers (ATC, Dielectric Labs) also offer specific broadband
> coupling capacitors, did you try them?
>
>        Gabriel

I have some samples of the Dielectric Labs parts, but have not tried
any since the cheap MLCC parts work well enough. I can't imagine that
the inductance could be much lower.

As shunt caps, all 0402 parts have too much series inductance to do
much good above a few GHz. The only difference between values seems to
be where the series resonance is.

Darrell Harmon


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