> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Mike Hord
> Sent: Monday, 23 June 2003 9:37 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [EE]: Power supply recommendations?
>
>
> >I wonder if you have considered active low pass filters?
> >
> >I have achieved some pretty impressive ripple rejection
> >by adding either a emitter follower capacitance amplifier
> >or a low pass op-amp.
>
> I have been puttering around with op-amps.  It'll be my next attempt, if
> the way I have it set up now doesn't work.
>
> I take it you're thinking setup a +/- 7 or 8 volt input from the
> noisy 12V,
> then use something else to make a precision +/- 5 V ref and run the
> signal from those references thru the LPF?  I like the idea in theory, but
> in practice, I'm starting to end up with a big honkin' PCB for what SHOULD
> be a tiny lil' circuit.
>
> But if that's the way it works, that's the way it needs to be done.

Ummm I could do an opamp regulator in ~ a postage stamp, use surface mount,
sot23 Vref something like a lm4050-5, a dual opamp that can supply say
5-10mA a few resistors and caps, you can use the first to buffer the Vref
for +5v, the second to invert the signal, a couple of tantalums and ceramics
for filtering and you are done :o)

Regards,

Kat.
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