[time-nuts] Super Regulator links
wb6bnq at cox.net
Thu Dec 13 23:25:51 EST 2007
This getting out of hand,
If you closely study the Andy weeke's circuit and the Walt Jung variation, you
will discover that it is VIRTUALLY the same circuit that is used in the UA723
regulator ! I suspect that Fairchild produced the UA723 before these guys
produced their work. It may be that Jung was involved with Fairchild, however, I
have no knowledge of that aspect.
I dare to speculate that the UA723 would be hard to beat as everything is
fabricated on the same die. Any so called circuit improvements, like those
claimed by Weeke can be applied to the UA723, or similar variations with equal or
I find it interesting that Weeke's, for example, publishes his explanation of
"his" circuit by fails, COMPLETELY, to provide any spec whatsoever ! He does,
however, provides himself with a way out by telling you it is very hard to make
these serious measurements, so don't this at home. I find that completely
Bruce Griffiths wrote:
> John Miles wrote:
> > What are some of your favorite low-noise regulators? When I made the remark
> > about the uA723, I was specifically thinking of its performance compared to
> > the LT1762. With Cref=5 uF, the uA723's output noise voltage is rated at
> > 2.5 uV from 100 Hz to 10 kHz. The LT1762, which seems to be among Linear's
> > quietest parts, is rated at 20 uV from 100 Hz to 100 kHz, with external
> > bypassing that places most of the noise at lower frequencies. Snake oil or
> > not, that's 18 dB less noise from the 723.
> This is perhaps a result of using the apparently inherently noisier
> bandgap style references which offer significant advantages (lower
> minimum input voltage, lower dropout but not necessarily lower noise) in
> lower voltage systems.
> > There are various hacks like Wenzel's that can clean up after a noisy
> > regulator
> That particular circuit is only effective over the 100Hz to 10kHz range.
> The brute force darlington buffered RC filter favoured by NIST is far
> more effective when the accompanying disadvantages are acceptable.
> > , but if there are quieter fully-integrated solutions out there I'd
> > like to hear about them. Posted back to the list in case there are other
> > views on the subject...
> > -- john, KE5FX
> I havent yet come across any IC that seems to approach the performance
> achievable with a 723.
> The next step up without adding too much complexity is perhaps to use a
> 723 with a low pass filtered LM329 reference powered from its regulated
> To improve the ripple rejection you can add an LM317 tracking preregulator.
> Beyond that a well designed discrete regulator is the only way to
> improve performance.
> Off course if you are building hundreds of circuits and dont want to
> take the risk of occasionally striking noisy parts then you either need
> to prescreen parts or buy noisier parts with guaranteed noise specs.
> Lots of so called low noise regulators pop up from time to time but when
> you actually read the datasheet and calculate the output noise for a 12V
> supply and not the 1V or so supply to which the noise specs apply they
> all seem to fall short of the 723's performance.
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