[sdiy] PCB layout tips

[Jay Schwichtenberg]

While we're on the subject of power bus/distribution I want to bring up a
pet peeve of mine. I look at so many designs and see little or no bypass
caps in a circuit. Anything that needs speed (which includes our VCOs and
VCFs) or is switching really should have at least small bypass caps. And if
they suck power some bigger caps should be put in with little ones. IMHO the
rules are: digital every chip or two, comparators always, analog depends on
the layout but every 2 or 3 chips, analog VLZ circuits on all the chips and
drivers put some bigger caps in there. Also the proper way of doing this is
power -> cap -> pin/pins not power -> pin/pins -> cap. The latter can in
some cases turn the lead from the pin to cap into an antenna or possibly
cause oscillations. It doesn't hurt to get the cap as close to the power pin
as possible. For grounding I usually don't do an overall star ground system
(if I did tubes I would). I take each sub-circuit (for example
inverter/summer or filter) and build a star ground for it and bring that out
to the main ground. Purists (audiophiles) will argue on doing star grounding
that way though.

Thanks for the soap box everyone.
Goooood holidays to one and all.
Jay

> -----Original Message-----
> From: owner-synth-diy at dropmix.xs4all.nl
> [mailto:owner-synth-diy at dropmix.xs4all.nl]On Behalf Of Scott Juskiw
> Sent: Sunday, December 15, 2002 6:16 PM
> To: synth-diy at dropmix.xs4all.nl
> Subject: [sdiy] PCB layout tips
>
>
> In AN-15 (Electronotes), BH suggests putting +ve and -ve supply lines
> in two parallel rows underneath the chips. This sounds like a good
> idea to me. Yet when I look at PCBs of various modules (from people
> on this list no less), I never see this in practice. Is there some
> reason why this is in fact a really bad thing to do?
>
> Is there a PCB layout "do's and don'ts" list available? Would anyone
> care to share any layout tips for a newbie?
>
>