Hi Oddly enough, if you use a tantalum electrolytic as C2, it's not very happy in that circuit. Their leakage with low voltages on them can be pretty nasty.
Bob -----Original Message----- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Poul-Henning Kamp Sent: Thursday, January 05, 2012 5:50 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Thunderbolt? (re simple gpsdo.) >> capacitors 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.