[sdiy] Negative voltage references

David G Dixon dixon at mail.ubc.ca
Sat May 19 18:28:35 CEST 2012


This whole discussion raises an interesting question (for me, anyway):
Under what circumstances is it important to have a reference of, say,
-5.000V, rather than, for example, a reference of -4.997V or -5.004V which
is nonetheless temperature-stable and rock solid?  In other words, given
that an opamp-derived reference would be rock solid and perfectly stiff, if
not necessarily perfectly accurate, when does this present a problem? 

I use REF02 in VCO circuits, but I never trim them for accuracy, because I
don't actually care if the reference is a few mV off one way or the other.
I simply want it to be dead constant with changing temperature.  In less
critical applications (VCAs, etc), I happily use 78L05/79L05.  Am I screwing
the pooch?



> -----Original Message-----
> From: synth-diy-bounces at dropmix.xs4all.nl 
> [mailto:synth-diy-bounces at dropmix.xs4all.nl] On Behalf Of 
> blacet at blacet.com
> Sent: Saturday, May 19, 2012 8:00 AM
> To: synthdiy diy
> Subject: Re: [sdiy] Negative voltage references
> 
> Yes, pos through an op amp; low offset maybe?
> 
> Lots of refs out there; look at the LM4040 series for 
> example. Various trimmed grades, one resistor, no cap.
> 
> > Hi all,
> >
> > What do people do for negative voltage references?
> >
> > Farnell list 1351 voltage references on their website, and 
> only one of 
> > them is negative (-10V).
> >
> > Are we expected to use a positive one and stick it through 
> an op-amp?
> >
> > Or should I just use a 3-pin negative voltage regulator 
> instead? It's 
> > not great, but it's cheap, and you can get negative ones 
> easily enough.
> > REF02's seem to cost £3-£4 each, which I regard as a lot of 
> money for 
> > the job. A separate regulator costs me £0.30 or so.
> >
> > All that talk about not using the rails for references must 
> finally be 
> > getting through to me! But unless I can find one, I'm in danger of 
> > slipping back into my bad old ways.
> >
> > Thanks,
> > Tom
> >
> >
> >
> >
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> >
> 
> 
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