Jim,

If you don't mind giving away some secrets, what was the general method you
used to achieve these numbers?  Not looking for schematics or anything,
just curious how you could get a switcher so quiet.

And also, how did you verify the -140db?  It seems to me not a trivial
achievment.

Tom

At 02:41 PM 6/25/04 +0500, you wrote:
> Lawrence,
>
> I agree 100% from a regulation standpoint.  But from a noise perspective,
> you'd be hard put to gain the same performance from such inexpensive
> hardware.   We have spent many manhours designing a power supply for a
> system we designed and build.   The noise performance for this system
> is around the -140+ (or should that be minus for lower noise)db range.
> This is not easily achieved by weither a linear type regulator or a
> switching type regulator.  We have achieved a small switching supply that
> has an input range of about 3 VDC to about 18 VDC with an output of
> plus and minus 5 AVDC @ ~200ma (each leg).  And this with a noise figure
> of better than -140db.   Not easily achieved, and not inexpensive, but
> doable.
>
> But as a practical matter, your design is sufficient for most lab uses
> you will probably run into in general work.   But if you have to have
> a very quiet supply, figure on spending a few more bucks than this.
>
>                                               Regards,
>
>                                                 Jim

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