[volt-nuts] How to keep voltage stable in the sub-100nV range?

[Scott Stobbe]

Depending on whether or not you care about DC, aluminum electrolytics can
be made to work by bootstraping. There is a Jim Williams app note for a 0.1
to 10 Hz preamp which recommends a $400 wet slug tantalum. Which is a tad
pricey, so I gave Bootstaping a 4700 uF electrolytic a try. It ended up
that impact of leakage noise/drift was below the input referred noise of
the auto-zero amp at 6nV/rtHz over 0.1 to 10 Hz.

On Wed, Nov 2, 2016 at 9:44 AM, David <davidwhess at gmail.com> wrote:

> On Wed, 2 Nov 2016 06:56:46 +0100, you wrote:
>
> >Hello David,
> >
> >On 01.11.2016 15:50, David wrote:
> >> avoid Mylar/polyester/PET and high dielectric constant ceramic
> >> capacitors.
> >
> >Do you have some specific recommendations/suggestions what to use?
> >
> >Polypropylene? PTFE? Wet Tantalum capacitors (extreme expensive)?
> >
> >Thanks,
> >
> >Andreas
>
> Wet tantalums might be the best for very long time constants but are
> useless for settling times below hours to days.  Some low leakage
> aluminum electrolytics are just as good.
>
> Charles pretty much covered it but I am not sure that polypropylene is
> always worse than polystyrene.  Some of the other plastic films are
> pretty good also but polypropylene is the most common high performance
> option.  Teflon is the best but is also expensive and has poor
> availablity.
>
> When I looked into this a couple months ago in connection with
> building a long time constant integrator for an analog only GPSDO, the
> primary limitation was insulation resistance of the capacitor.  Even
> the best low dielectric constant C0G/NP0 capacitors were much worse
> than polypropylene film which was itself was much better than
> polyester.
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