[sdiy] PCB layout question

harrybissell at wowway.com harrybissell at wowway.com
Tue Nov 4 19:03:45 CET 2008


I use a .1uF / 50V axial lead ceramic (X7R) on every IC power pin
to ground. Thats two per standard op-amp.

Think my twin-brother-separated-at-birth (Jim Patchell) uses the same
scheme.

MORE of the game is proper power supply routing on the PCB.  I layout
the power bus before ANY other components go on the board.

 "If it needs to be stronger, we make it bigger. If that makes it
ugly, we chrome it."
-- Harley-Davidson engineer, speaking anonymously during
discussion of structural engineering and materials science.

H^) harry  (director of overkill engineering :^)



On Sat, 01 Nov 2008 20:45:22 -0700, David G. Dixon wrote
> Paul,
> 
> Perhaps you can enlighten us, then, on the delicate art of seasoning 
> pcbs with bypass caps...?  Please, help us to parse our power-rail punctuation!
> 
> David G. Dixon
> Professor
> Department of Materials Engineering
> University of British Columbia
> 309-6350 Stores Road
> Vancouver, B.C.  V6T 1Z4
> Canada
> 
> Tel 1-604-822-3679
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> 
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> -----Original Message-----
> From: synth-diy-bounces at dropmix.xs4all.nl
> [mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of Paul Perry
> Sent: Saturday, November 01, 2008 5:00 PM
> To: Synth-diy at dropmix.xs4all.nl
> Subject: RE: [sdiy] PCB layout question
> 
> Bypass caps are like commas in writing, or salt in cooking.
> 
> Some people sprinkle them in at random, hoping it will help somehow.
> Others, who understand their function, know exactly when and where 
> they are needed. Incidentally, while it is true that the bypass caps 
> might not appear to make much difference at audio frequencies -
>  sometimes if you leave them out, you will find RF oscillations! 
> Unsurprising, with transistors having 200Mhz cutoffs.
> 
> Is decoupling and bypassing a black art? Yes, if you do it in the dark.
> 
> paul perry Melbourne Australia
> 
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Harry Bissell & Nora Abdullah 4eva




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