[sdiy] dare I say - decoupling?

[harrybissell]

Hello Michael

~safe~ to mention decoupling ? only if you are willing
to see what crawls out of the woodwork ??? :^P


> which is better, decoupling caps from each rail to ground, from rail to
> rail, or both?

IMHO its from rail to ground.  Most currents in the devices flow from
one or another rail to ground.   There may be some rare cases where
rail to rail might be better... (I think JH pointed out one such case a
while
back)

> what's the difference?

You want to have the decoupling cap where it is available to deliver
current
to the load (output) with the minimum of series inductance. This is why you
locate them as close as possible to the IC pins, and with a minimum 'loop'
area.

Remember those funny sockets with the decoupling caps built in (mostly for
digital ICs) ???  How much shorter can you make the connection than a
straight
line ?

>
>
> what is the air-speed velocity of an unladen swallow?

err... African or European ???

H^) harry

>
>
> thanks in advance oh wise ones ;-)
>
> M. A. Ruberto