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.BruceBrooke 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.
LowNoiseLM723Regulator.pdf
Description: Adobe PDF document
_______________________________________________ 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.
