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Date:	Sun, 15 Feb 2015 21:19:28 -0500
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Subject:	Re: [geda-user] Commonness of internal layer cutouts/cavities?
From:	Evan Foss <evanfoss AT gmail DOT com>
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I use them all the time when I make trans-impedance amplifiers for
things like photodiodes and other sensors.

On Sun, Feb 15, 2015 at 10:01 AM, Bob Paddock <bob DOT paddock AT gmail DOT com> wrote:
> On Sun, Feb 15, 2015 at 9:08 AM, Jason White
> <whitewaterssoftwareinfo AT gmail DOT com> wrote:
>> How common are cavities (that is internal cutouts on a PCB specific to
>> a single layer) in the electronics world?
>
> Common, no.  Sometimes required, yes.
>
> For example in some applications you don't want a plane under an
> op-amp because of the stray capacitance to the plane causes
> oscillations.
>
> Sometimes you need a slot for isolation reasons, such as under an opto-coupler.
>
> On the other hand it is best to avoid slots and cutouts because of the
> increase in EMI they cause.
>
> Always trade offs. :-(



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