Super Regulator, collecting the facts

[janneman]

Originally posted by peranders
The PSRR is different at the positive vs. negative supply pin.

Hmmm. Yes. Never thought about that. You may have apoint there.

Jan Didden

[jackinnj]

In the "Improved" version with the LM317/337 pre-regulator there's only 2.3 Volts dropped across the Super-Regulator -- this should require a much smaller heat sink than 9 C/W.

[janneman]

Originally posted by jackinnj
I don't have an Audio Precision to make the noise measurements, but hooked up the HP3581A (which has 100 nanovolts lowest scale) to the Super Regulator with the Old Colony boards, zener instead of 1N4148 and an AD825AR on a high quality adapter and AD797AN. There is no pre-regulator for either setup:

Interesting. Any idea why that curve shoots up at 40kHz or thereabouts? Is this a measurement artifact?

Yes, that 797 is pretty good. It's just that it often seems difficult to get it stable in these regs.

Jan Didden

[jackinnj]

Originally posted by janneman



Interesting. Any idea why that curve shoots up at 40kHz or thereabouts? Is this a measurement artifact?

Yes, that 797 is pretty good. It's just that it often seems difficult to get it stable in these regs.

Jan Didden

Jan I deleted the picture -- the WJ/JD articles used a constant Q filter which would should show a rising 3dB slope as WJ explained in 2/95 -- the HP3581 is constant bandwidth and I was trying to keep the BW as a % of the CF relatively constant -- the narrowest is 3 Hz -- but this is 30% of the lowest frequency and only 0.006% of 50kHz. In any case, I didn't want to mislead -- I will show the data in the graph below and it is really only useable as a relative assesment since the HP3581 has some nV of noise which can't be eliminated -- I thought there was an artifact as well, but the data is repeatable. Again, the Oreo cookie tin was used to good effect.

[peranders]

Are you able to do some weighted measurements like DIN-A or something?

[jackinnj]

P-A -- I want to crank up the calorimetric true RMS meter first -- I just repeated the measurements again with the LT1055, and redid the AD797 -- I will have to look through my opamp box for more single JFET devices to test out.

[peranders]

Do you use LM329 + 1k+ 100 uF as voltage reference?

[jackinnj]

I use LM329DZ + 4.99K + 120uF/25V

[peranders]

Is your LP-filter 5k+100uF ?

[jackinnj]

There are a pair of 1K resistors which determine the error signal fed to the inverting input. The Voltage Reference is driven from the Positive Sense pin -- all of this is on a stock Old Colony board -- the only exception is that the filter capacitor which used to be on the positive supply pin is now across the diode to the collector of the 2N5087, and a zener is used instead of a 1N4148.

With respect to the noise -- I want to remake the calculations using some different equipment -- I have two filter setups which are not part of the graphs -- a 100 milliHz to 10 Hz filter which TI uses when characterizing the TL431, an a 10Hz to 100kHz filter which Linear used in Application Note 83"Performance Verification of LDO Regulators". I use these with the HP3403 true RMS meter which uses a thermopile, not a log-antilog RMS detector.