[sdiy] PCB layout rules

[Antti Huovilainen]

On Fri, 22 Dec 2006, Seb Francis wrote:

> 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.

No. The cap steadies the power supply lines, not the ground (ground is 
where everything is referenced to). And since it acts as short circuit for 
high freqs, a spike in the power supply line would get coupled through the 
cap to ground and possibly contaminate it for other signals.

This is partly why I'm interested in the sense/force ground. Such 
decoupling caps would be connected to force ground while the sense ground 
would be used for reference (such as + input of inverting opamp).

Antti

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