Poul-Henning Kamp wrote:
In message<[email protected]>, Brooke Clarke writes:
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
If you really want to get low noise, you do the "amplify noise by -1"
trick.
Vicor has a special "afterburner" module you can hook after their
switchers, which does this.
The trick is that you don't really need much power in the amplifier,
it just have to be able to cancel out the noise, a trivial transistor
or op-amp will do.
If you really want to go radical, take a peek at Nationals AN1651,
study the two opamps at the top of the schematics...
Poul-Henning
The 30uV/rtHz and greater noise (produced by U4 and U5) below 1Hz due to
the 1M series resistor plus the amplified power supply noise for
frequencies below 1Hz or so are a little high for some applications.
Bruce
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