[sdiy] filter cap needed?

[Seb Francis]

David G. Dixon wrote:
> Thanks to all for your replies.  I understood the basic idea about switching
> transients.  I guess I'm just not convinced that putting the caps adjacent
> to IC power pins is significantly better than putting them an inch or so
> away on the power rail, near the ends of ICs.  I'd appreciate any comments
> in this regard.  If it looks like this would make a significant difference,
> then I might have to change my ways...
>   

I doubt an inch will make any difference for analog stuff with 
reasonably sized traces.

I assume you're talking about thru-hole, so another way is to solder a 
little axial multi-layer ceramic across the power pins on the back of 
the board.  I believe you can also get IC sockets with de-coupling caps 
built in.

For SMT designs it's usually easy just to put a small chip capacitor 
right by the power pins.

Seb