Super Regs

[AndrewT]

K,
is there a post detailing your measurement system?
1uV to 10uV is mighty impressive.

[jackinnj]

would be useful if the Y-axis was in dBV. Is the instrument's noise floor (for comparison) shown in slide #1?

[klewis]

Originally Posted by AndrewT

K,
is there a post detailing your measurement system?
1uV to 10uV is mighty impressive.

I'm using an Hp3562 spectrum analyzer. It's connected to my computer via HPIB. The screen shots are from a Vee program I wrote to capture and display the data. The setup for the test is to take the output of the voltage regulator into the 3562 which is set for AC & Gnd coupling, power spectrum, Mag - linear, vlts/sqrtHz (so, the vertical units are in uVlts/sqrtHz). As usual, Andrew's questions get me thinking. Just ran it again with the units changed to Vrms and the scale jumped up. So, measured in Vrms I get around 9.9uVrms and 89uVrms at the 10kHz spike. I will repost plots in a bit.

Ken

[klewis]

Plots with vertical scale at Vrms. First plot is overall bandwidth 0 to 100kHz second plot is limited bandwidth 0 to 2kHz. I have put a common mode choke and film cap in line prior to the regulator which killed any 60hz related artifacts.

Ken

[klewis]

Finish my build of Per-Anders SSR-02. Results at 0-100k look very nice, note the vertical scale is 0 to 10uVrms. But, when looking at 0-2k, not so nice. Regulator is fed from identical supply configuration as the LME49600 regulator. It is not placed in a shielded box, but, neither was the LME regulator. Maybe I have something wrong...

Ken

[jackinnj]

The very high gain of the SR means that they are susceptible to excitation. That's why some have had issues with the AD797 in this application.

For noise measurements, you should really use a battery. The battery and regulator and any local amplifier should be shielded and grounded.

You should also baseline the measurements -- to get a handle of the SNR of your system.

attached is a snapshot of a run I did for the Sjostrom regulator last March

Left scale is nV/RtHz

[klewis]

Originally Posted by jackinnj

The very high gain of the SR means that they are susceptible to excitation. That's why some have had issues with the AD797 in this application.

For noise measurements, you should really use a battery. The battery and regulator and any local amplifier should be shielded and grounded.

You should also baseline the measurements -- to get a handle of the SNR of your system.

attached is a snapshot of a run I did for the Sjostrom regulator last March

Left scale is nV/RtHz

But Jack, if it can't filter out 60hz fundamentals, why use it? The LME48600 setup is quite clean relative to 60hz fundamental. And it was tested exactly the same way. It has other problems... which I will try to address with a new layout.

Best,

Ken

[jackinnj]

Originally Posted by klewis

But Jack, if it can't filter out 60hz fundamentals, why use it? The LME48600 setup is quite clean relative to 60hz fundamental. And it was tested exactly the same way. It has other problems... which I will try to address with a new layout.

Best,

Ken

Because, that's a separate measurement -- "Line Rejection" - in which you inject a swept sine voltage into the input of the regulator and measure how much the circuit attenuates the perturbation.

Take a look at Walt Jung's articles -- archived on his site Home

[DDB]

Walt Jung has recently posted part four of his 1995 SuperReg series by Gary Galo for those interested. http://waltjung.org/PDFs/Regs_for_High_Perf_Audio_4.pdf

[klewis]

Originally Posted by jackinnj

Because, that's a separate measurement -- "Line Rejection" - in which you inject a swept sine voltage into the input of the regulator and measure how much the circuit attenuates the perturbation.

Take a look at Walt Jung's articles -- archived on his site Home

Thanks Jack.