Looks very nice Jack, I'm looking forward to some results from you. I've looked into using a high performance opamp buffer in a different regulator as well, but then dropped the idea. Is the lm4040 a reasonably low noise reference in reality? I have no experience with it.
I wanted to use what I had on hand -- and the one reference I had in SOT-23 was the LM4040 which, by coincidence, Nat Semi used as well. I also used through-hole rectifiers!
Will see how we do when the stuff comes back. I have stock Super Regulator boards from Old Colony to compare noise, impedance etc.
Will see how we do when the stuff comes back. I have stock Super Regulator boards from Old Colony to compare noise, impedance etc.
It would be interesting to see what this little cap could do practically. It was a long time since I tested AD797.You read my mind or what?
I just read a comment by Scott Wurcer, the designer of the 797, here:
http://www.diyaudio.com/forums/showthread.php?postid=1509264#post1509264
Wish I had know that at the time...
Jan Didden
It's the design from the LME49600 datasheet, nothing original there. The open loop bandwidth of the LMe49600 is 110MHz (180MHz if the bandwidth pin is brought to Vee).
I strongly suspect that it is a layout issue, since all of the connections are correct per the schematic. I did have a layout issue with the SOT-23 LM4040 which I fixed.
National also recommends bypassing the LME49600.
I can put in a modified ground scheme with copper tape.
Unlike the Super-Reg -- I don't see how this one starts if you attempt to feed it from the regulated side. In the Super Reg there is current flowing to start it going.
there is a whole section on start up.
It's inherent in the design.
You too must design for self starting.
There are others that cannot do this and then he/she organised a Group Buy with a non reliable starting and oscillating regulator.
It always amazes me how things happen sometimes in the real world. There are huge GB started on projects that aren't anywhere near stability/completeness, and then there are well tested and performing circuits and nobody's going for those. Puzzling.
Well, forget about the LME49600 Regulator -- here are some results --
A Weighted level measurements -- a.c. coupled with 15mA load -- shielded by my Oreo Cookie Tin:
78L15 (ST Micro) RMS 26.9uV, Quasi-Peak 44.3uV
LM317 (National, No adj bypass) RMS 181uV, Q-Peak 289uV
Super-Regulator (LT1028 error amp) RMS 2.2uV, Q-Peak 3.6uV
LME49600 (LM4040 Ref) RMS 347uV, Q-Peak 564uV
My advice to you, young man, get the Super-Reg boards from Old Colony and stop wasting your time.
The Super Reg is only slightly noisier than the battery.
A Weighted level measurements -- a.c. coupled with 15mA load -- shielded by my Oreo Cookie Tin:
78L15 (ST Micro) RMS 26.9uV, Quasi-Peak 44.3uV
LM317 (National, No adj bypass) RMS 181uV, Q-Peak 289uV
Super-Regulator (LT1028 error amp) RMS 2.2uV, Q-Peak 3.6uV
LME49600 (LM4040 Ref) RMS 347uV, Q-Peak 564uV
My advice to you, young man, get the Super-Reg boards from Old Colony and stop wasting your time.
The Super Reg is only slightly noisier than the battery.
The documention can be found if you click at the links
Have you checked Walt Jung's webpage. All you have to know is there.
Oh, then unless you used the same reference device for each of them I'm afraid we're comparing apples with oranges. No?
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