Hi There's actually a prior paper on the "figure 1" amp.
Bob On Sep 5, 2012, at 6:38 PM, David <[email protected]> wrote: > It is even more difficult when the schematic is wrong like in figure 1 > where the emitter and collector of the PNP are reversed. > > On Wed, 5 Sep 2012 16:26:04 -0600, Tom Knox <[email protected]> > wrote: > >> >> 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.
