Super Regulator, collecting the facts

[unixdeveloper]

Hello Per-Anders,

I am also not able to send you an email. It takes me to the support center.

Thanks

[jackinnj]

Did some op-amp rolling with the SR -- LME49710 and OPA134 look pretty good, but the LT1028 doesn't seem to work well in this application.

[peranders]

Which board did you use? Output voltage?

[ticknpop]

I believe there is a version of the Jung super regulator with film caps rsther than electrolytics - any one seen or heard it or know what circuit values are changed?

[qusp]

sounds like it could be quite prone to oscillating, many regulators need to see some ESR

[jackinnj]

Originally Posted by peranders

Which board did you use? Output voltage?

I used the board which Jan designed, I will call it "the Reference Board". The output voltage was +/- 13.7 VDC and the load 137mADC + 50mA AC. Right now I have an AD825 on my Sjostrom board and I will have to get the rework station out to look at the other opamps.

You can get the Zout down into the low 20's of micro-Ohms @100Hz -- with the AD797, however, the Zo is in the low teens. 9Jung was able to measure in single-digits.)

With regard to the caps -- the Panasonic HFQ's are no longer available the 120uF/25 V had ESR of 200milliOhms, the FC's have ESR of 250milliOhms. ESR is important in the stability of the SR.

[peranders]

Didn't you use LT1028 before with excellent results?

[ticknpop]

Actually the film version was designed to get rid of the dielectric absorbtion of the electrolytic capacitors and doesn't osscilate, but might if one subbed the wrong components or had a bad board layout problem.

[janneman]

Originally Posted by ticknpop

Actually the film version was designed to get rid of the dielectric absorbtion of the electrolytic capacitors and doesn't osscilate, but might if one subbed the wrong components or had a bad board layout problem.

The film version came into being because people said that film caps were better because 'everybody knows they are better'.
However, the smart thing to do is always to select components for the application you want to use them for.

Film caps in decoupling circuits together with other reactive circuit elements like wiring L lead to local oscillations.
So, using film caps here is ill advised; you can only decouple and damp if you remove energy and that's what an electrolytic does very well. You NEED the absorbtion factor to decouple and damp any ringing.
Film caps do this much less so you end up using the wrong cap and compensating for it with yet another network of a C and an R in the form of a snubber.

jan didden

[ticknpop]

Thanks Jan. i heard there were some film cap versions around , but didn't get all the story.