Hi For extra added “Time Nut” grade fun:
Clip the collector lead off of the SOT-223 packages (between emitter and base leads). You probably will gain a couple of db of isolation. (running common base). Bob > On May 11, 2016, at 8:24 PM, Bob Stewart <b...@evoria.net> wrote: > > Hi Bob et al, > > I'm finally drawing up a schematic for a DMTD and I thought I'd use the NBS > circuits for a lot of it. So, how about PZT3904 transistors in the isolation > amps? They're in SOT-223 with the heat sink tab. > > I figure to use some version of the TUF-1 for the DBMs. The first version > will be a bit breadboardish. I'll use the PRS-45A as the reference > oscillator and the 8640B as the offset oscillator. If it's workable, then I > thought I'd put an Analog Devices DDS onboard with a small PIC to set it up. > I haven't gotten as far as the zero-crossing detectors yet, but I was > thinking of using 125 gates. > > Bob > -------------------------------------------- > On Tue, 3/29/16, Bob Camp <kb...@n1k.org> wrote: > > Subject: Re: [time-nuts] high rev isolation amps > To: "Discussion of precise time and frequency measurement" > <time-nuts@febo.com> > Date: Tuesday, March 29, 2016, 6:08 PM > > Hi > > There were (and maybe still are) SOT-89 versions of the > 2N3804 and 3906. They will handle more > power than most of the other versions. That gives you better > Vce on the string. They also have less > package inductance which helps tie the base to ground. If > you are building some of those circuits, they > are worth looking for. > > Bob > >> On Mar 29, 2016, at 6:47 AM, Charles Steinmetz <csteinm...@yandex.com> > wrote: >> >> See below for schematics of the NIST isolation > amplifiers from 1990 and 1997. NIST reported the > isolation as >120dB. >> >> I built isolation amplifiers similar to these (with > lower-noise power supplies and biasing tinkered slightly for > better dynamic range), and with careful construction > achieved isolation substantially better than 120dB (see my > post of 11/25/14 for more details). >> >> Best regards, >> >> Charles >> > <NIST_120dB_isolation_amplifier_schematic_email.gif><Iso_amp_NIST_schematic_with_values_5MHz_1997_email.gif>_______________________________________________ >> 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. _______________________________________________ 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.