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 <[email protected]> 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. > _______________________________________________ > volt-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/volt-nuts > and follow the instructions there. > _______________________________________________ volt-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
