[sdiy] Analog & Digital Ground

[Seb Francis]

Ian Fritz wrote:
> At 11:09 AM 4/11/06, Seb Francis wrote:
>> Now that Harry has enlightened me to think in terms of return path 
>> for currents, I can see that when sub-circuits interconnect the 
>> ground impedance between these should be low as possible.
>
> The beads don't have any impedance at dc and audio frequencies.

But if you have an interconnection between the digital circuit and 
analog circuit, then the voltage presented to the analog circuit is 
going to be relative to the digital ground.  If you have HF spikes 
existing on the digital ground relative to the analog ground then aren't 
these spikes going to couple into the analog circuit via the 
interconnection?  Maybe not, I don't know?

Seb