[sdiy] Analog & Digital Ground

[Ian Fritz]

At 12:36 PM 4/11/06, Seb Francis wrote:

>>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.

That is why you want to isolate the digital circuit at rf -- so there is no 
signal from the switching on the ps lines.

(OK, I lied, I'm going to say it again.)  The beads don't have any 
impedance at dc and audio frequencies.


>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?

No, the beads isolate the grounds at rf, so the spikes do *not* 
couple.  That's what the beads are for.

   Ian