[sdiy] PCB layout question

David G. Dixon dixon at interchange.ubc.ca
Tue Nov 4 19:21:23 CET 2008


Harry,

That's pretty much what I figured most people did, as this would seem to
neutralize the problem, rather than attempting to solve it.  I mean, there's
really not much more one can do than to put bypass caps on every IC, is
there?  It seems a pretty small price to pay for insurance!

Cheers,
Dave


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
Fax 1-604-822-3619
 
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-----Original Message-----
From: harrybissell at wowway.com [mailto:harrybissell at wowway.com] 
Sent: Tuesday, November 04, 2008 10:04 AM
To: David G. Dixon; 'Paul Perry'; Synth-diy at dropmix.xs4all.nl
Subject: RE: [sdiy] PCB layout question

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
> Fax 1-604-822-3619
> 
> "PERFECTA FINGAMUS SERVIAT NATURA"
> 
> The information in this email and in any attachments is confidential 
> and intended solely for the attention and use of the named 
> addressee(s).  It must not be disclosed to any person without the 
> writer's authority.  If you are not the intended recipient, or a 
> person responsible for delivering it to the intended recipient, you 
> are not authorized to and must not disclose, copy, distribute, or 
> retain this message or any part of it.
> 
> -----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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