Hi Bob; There are many designs I have seen employed at NIST that have low phase noise and low noise floor. But it is often not that easy to build a working prototype that actual achieves those levels of performance. power supply design, parts layout, shielding, and part selection all play a substantial role in achieving that level of performance.
Thomas Knox > From: [email protected] > Date: Wed, 5 Sep 2012 18:05:41 -0400 > To: [email protected] > Subject: Re: [time-nuts] REF osc distribution. > > 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. _______________________________________________ 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.
