[sdiy] strange pcb layout practice.

[jhaible at t-online.de]

Low impedance.

There is nothing such as "0 Ohm" in real life.

And you never have the same voltage at every point
of a groundplane, either.

Currents on the GND connections must be directed
as much as other signals to avoid unpleasant side
effects. They always follow the path of lowest energy,
and it's the work of the designer to make the desired
current route the lowest energy path.

This is valid for both, HF and low frequency design:

At DC, lowest resistance directs the current flow.

At modest frequencies, inductance can be as important.

At high frequencies, the GND current tries to follow the
signal current. (Forget this last point for audio applications.)

JH.




Nils Pipenbrinck schrieb:
> Hi there.
> 
> I just had a view on a Korg Trinity output board (a 
> friend of mine has to 
> resolder the jacks). I took a look at it and found 
> something, that makes me 
> wonder:
> 
> On the pcb there are several places where they use 0 ohm 
> resistors to 
> connect one ground trance with the other - no problem so 
> far, it's a single 
> sided pcb, so they have to bridge here and there. What I 
> don't understand 
> is, that they don't use one single jumper but 10 in 
> parallel. 
> 
> They do this most of the time if they "bridge" over a 
> signal trace. 
> 
> But why the hell are they using 10 or more bridges, and 
> not just one? Is 
> this one of those tricks I don't know about? Is this good 
> practice if you 
> don't want RF signals to stray into the signal?
> 
> Maybe someone knows why they do this? I can't see a good 
> reason. 
> 
> 
> 	Nils Pipenbrinck
> 
> 
>