On 8/13/08, Spehro Pefhany <speff@interlog.com> wrote:
> At 07:26 AM 8/13/2008, you wrote:
>
> >Hi list,
> >I asked a question about low noise, high gain amplifier design a
> >couple weeks ago.  I've been doing a lot of reading on everything I
> >can find on the subject.  One thing I understand is proper PCB
> >layout is important, but most articles mention this but give no
> >detail.  Can some please explain what is meant by using a "star
> >ground" such as in this article?  I was going to use a ground plane
> >but may that is not a good idea.
> >Thanks,
> >FJ
> >http://instruct1.cit.cornell.edu/Courses/ee476/ideas/singlesupply.pdf
>
> A "star ground" is where all the ground lines run to a common point,
> like the lines of an asterisk (*).
>
> A ground plane may not be as good as a star ground, depending on the
> details.

 Using a star ground you have control on the current flow. A massive
ground plane is unpredictible from the currents flow perspective.
Sensitive PLL circuits in RF applications are always using star
grounds. A ground plane become a pseudo star ground using many vias
placed in the right places and optimal isolations in the copper plane
(splitted copper plane, not different ground planes isolated between
them).

Vasile
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