Hi The NIST bipolar designs can indeed do better than a good quality OCXO for short term and close in phase noise. If you have a wide band floor at -185 dbc/Hz on your OCXO they aren't quite up to that level.
Bob On Sep 5, 2012, at 5:55 PM, Tom Knox <[email protected]> wrote: > > I have seen that many commercial ref distribution amps are not as good as a > quality low phase noise 5 or 10MHz oscillator, considering the time and > resources that went into their design > I think it would be difficult to design a amp capable of distributing > something much cleaner then a LPRO. > Thomas Knox > > > >> From: [email protected] >> Date: Wed, 5 Sep 2012 17:37:34 -0400 >> To: [email protected] >> Subject: Re: [time-nuts] REF osc distribution. >> >> Hi >> >> You *can* get the job done with a CMOS inverter biased up and filtered. An >> op amp is likely not as good as the full bipolar approach and may be better >> / worse than the gate depending on exactly what you are looking at. >> >> Bob >> >> On Sep 5, 2012, at 12:59 PM, Michael Tharp <[email protected]> wrote: >> >>> On 09/05/2012 12:46 PM, Bob Camp wrote: >>>> Hi >>>> >>>> There are a number of discrete transistor buffers that have very good >>>> isolation and short term stability / phase noise performance. I'd take a >>>> look at the one from the NIST papers and Bruce's more modern re-design. >>>> All >>>> are in the archives. http://tf.boulder.nist.gov/general/pdf/498.pdf is a >>>> pretty good place to start. >>>> >>>> Mostly what they do is to run a common emitter amplifier followed by >>>> several >>>> common base amplifiers. They may or may not follow that with a buffer. Each >>>> channel gets a separate string of amplifiers. All the common emitter amps >>>> are driven in parallel by the reference source. >>>> >>>> The transistors used are normally cheap stuff like the 2N3904. Except for >>>> the power supply nothing in the circuit costs much. None of it is hard to >>>> find. >>> >>> For an integrated (op-amp) solution, how does OPA830 stack up? I'm trying >>> one out for a GPSDO design to buffer the signal from the OCXO for 50 ohm >>> output, but I may also build a distribution amplifier at some point. >>> >>> At $1.91 for single pieces on Digi-Key it's not terribly expensive, but >>> something cheaper could probably get the job done. There are also dual and >>> quad versions (OPA2830 and OPA4830). >>> >>> -- m. tharp >>> >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >> >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
