[sdiy] Analog & Digital Ground

[Seb Francis]

>> In figure 20 (shows how ferrite beads and decoupling caps are used in 
>> combination to localise high frequency circuits) there is only a bead 
>> shown on the power rail and not on the ground.
>
> Figs 15, 16, 19, 21 and 24 all show a bead in the ground line.  (The 
> implication is that fig 15 is proper if there is not a large dc 
> component).  I think in terms of fig 21 for isolating separate 
> circuits on a single board, but I haven't done comparative tests of 
> different configurations.  Maybe it's an overkill.
>
>

Do you not think that Harry's point is valid about interconnecting 
circuits needing a low impedance (at all frequencies) ground connection 
between each other?


> Anyway, let us know how this works out in your application.
>
In my mind (in theory only!) I think I should put a ferrite just on the 
power rail, but probably I will leave some PCB space for a ferrite on 
the ground as well just to see if it makes a good or bad difference.

At least I feel somewhat clearer on the whole thing following this 
discussion :)

Seb