Bruce, Why not just use a diode in place of the 2M3904 circuit ? Seems like it would do the same thing with less parts.
Also, would not the Texas Instruments TL-431 be a better choice as it has a lower noise spec them the LM329 part. In addition, with its adjustable nature, the TL-431 would be adjusted to make sure the single diode (in place of the 2N3904 circuit) is shut off when the TL-431 comes up to speed. Obviously, this would be best with intended output voltages above the reference level. Bill....WB6BNQ Bruce Griffiths wrote: > I meant something like the attached circuit schematic for an LM723 based > 15V regulator. > The circuit can be easily extended to use an external pass transistor > where more current is needed. > > The LM329 is biased from the regulator output which improves the > reference line rejection. > The 723's internal reference is used only during startup. > The 2N3904 disconnects the internal reference when the LM329 terminal > voltage exceeds about 5.4V. > Some optimisation of the circuit may be required. > > Bruce > > Arnold Tibus wrote: > > Hi, > > > > NS gives some informations about improvements in their AN-173.pdf > > http://www.national.com/ds.cgi/LM/LM117.pdf > > Audio freaks are discussing it in > > http://www.diyaudio.com/forums/solid-state/28978-improving-lm3x7-regulator-circuit.html > > Is that what you are looking for? > > > > 73 > > Arnold > > > > > > On Thu, 25 Feb 2010 11:22:02 +1300, Bruce Griffiths wrote: > > > > > >> You can improve the performance of the LM723 if one substitutes an LM329 > >> for the internal reference biased from the regulator output. > >> The trick is to use the internal reference for startup and decouple it > >> with a diode or similar once the LM329 achieves its nominal output. > >> > > > >> Currently, there appear to be 2 variants of the LM723 one (made by > >> National) that uses a noisy bandgap reference and another variant that > >> actually uses a quieter zener reference. > >> > > > >> Bruce > >> > > > >> Brooke Clarke wrote: > >> > >>> Hi neville: > >>> > >>> My old Gibbs rack mount 5 MHz standard used the LM723 linear > >>> regulator. I believe it's one of the lowest noise regulators you can > >>> use. > >>> http://www.national.com/mpf/LM/LM723.html#Overview > >>> > >>> Have Fun, > >>> > >>> Brooke Clarke > >>> http://www.PRC68.com > >>> > >>> > >>> Neville Michie wrote: > >>> > >>>> Hi, > >>>> I remember a reference, probably by Bruce, that LEDS provide a low > >>>> noise voltage reference. > >>>> I am proposing to build a voltage regulator for a thermally > >>>> controlled LPRO rubidium oscillator, > >>>> with the voltage regulator being mounted on the 0.5 inch thick > >>>> aluminium heat sink plate. > >>>> The LEDS would also be mounted on the plate, which has controlled > >>>> temperature. > >>>> The LPRO has internal voltage regulation, and by running it at ~40C > >>>> and 18Volts, the thermal > >>>> flux within the unit is minimised as is the power demand. > >>>> What I want to know is if a LM317 running on a stack of LEDs driven > >>>> by the LM317 output > >>>> would provide a low noise power source? What would be better? > >>>> > >>>> cheers, Neville Michie > >>>> > >>>> > > > > > > > > _______________________________________________ > > 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. > > > > > > ------------------------------------------------------------------------ > Name: LowNoiseLM723Regulator.pdf > LowNoiseLM723Regulator.pdf Type: Portable Document Format > (application/pdf) > Encoding: base64 > > ------------------------------------------------------------------------ > _______________________________________________ > 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.
