[sdiy] PCB layout rules

[John Luciani]

On 12/22/06, Seb Francis <seb at burnit.co.uk> wrote:
> Antti Huovilainen wrote:
> > On Fri, 22 Dec 2006, Harry Bissell Jr wrote:
> >
> >
> >> One per IC power pin per voltage... so the tpyical
> >> opamp gets two.
> >>
> >
> > Doesn't this mean that the ground might get contaminated by power supply
> > noise? From what I've understood, a cap is only needed between the rails
> > for stability.
> >
> >
>
> Isn't that the point of the cap that the ground doesn't get contaminated
> - the very fast current spikes are sourced/sinked from the capacitor not
> the ground trace.

Yes. Both the power supply trace and the ground trace would ring.

> But I guess the optimal place for the decoupling cap(s) really depends
> on the IC itself and where the current is flowing to/from.

There is a very good application note from Analog Devices about grounding
and decoupling called  "An IC Amplifier User's Guide to Decoupling,
Grounding,. and Making Things Go Right for a Change" which is  by Paul
Brokaw.

http://www.analog.com/UploadedFiles/Application_Notes/135208865AN-202.pdf

(* jcl *)

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