Thanks. Me too: now I got it, sort of bootstrap and now I see that R2 is needed because the real filter is R2*C2 and the leakage is not totally compensated if C1 has to move to a new value -> R*C1<R2*C2.
On Fri, Jan 6, 2012 at 12:00 AM, paul swed <paulsw...@gmail.com> wrote: > Poul > Thanks have been kind of following this thread and the diagram did not make > a lot of sense. > I figured I missed part of the thread. But this clears it up nicely. > Regards > Paul. > WB8TSL > > On Thu, Jan 5, 2012 at 5:49 PM, Poul-Henning Kamp <p...@phk.freebsd.dk > >wrote: > > > In message <CAL8XPmO76XuTETZC=33_v2YWuJGcw8gCvtTDHyae6E4MFb18= > > g...@mail.gmail.com> > > , Azelio Boriani writes: > > > > >I have googled extensively trying to find something about the dual > > >capacitor method of reducing the leakage current... nothing found. > Please, > > >can you indicate anything for me to learn more? > > > > It is very simple: > > > > R1 charges C1 to the DC potential and therefore C2 sees > > (almost) no DC voltage, which means (almost) no leakage > > current. C2 is still a capacitor for any AC or dV component. > > > > I belive I picked this trick up from a datasheet or app-note relating > > to precision voltage references. > > > > Poul-Henning > > > > >> [Some op-amp] >-+-----R2-----+--> > > >> | | > > >> | ----- C2 > > >> | ----- > > >> | ____ | > > >> +---|____|---+ > > >> R1 | > > >> | > > >> ----- C1 > > >> ----- > > >> | > > >> GND > > > > -- > > Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 > > p...@freebsd.org | TCP/IP since RFC 956 > > FreeBSD committer | BSD since 4.3-tahoe > > Never attribute to malice what can adequately be explained by > incompetence. > > > > _______________________________________________ > > time-nuts mailing list -- time-nuts@febo.com > > To unsubscribe, go to > > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.