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.
