Super Regulator

Overview

The super regulator has a very rich history. These pages give a nice overview of the whole thing. Do yourself a favor, and go read them.

Schematic

I had some more wishes than just to have a well regulated voltage. Because of the amplifier the regulator was going to power, I wanted to have a close match between the positive and negative voltage. Due to variations in components, two separate regulators can end up with differences in the order of one volt — several percent of the intended voltage. My solution was to include a pot (R10) that allows me to adjust the position of the ground between the positive and negative rail. The voltage between the rails is fixed. I used a 25-turn precision cermet trimmer pot, allowing me to tune the voltages to match eachother to the accuracy of my voltmeter.

LSP17 and LSP18 allow me to connect the 3 V LED in the switch. LSP3 should be connected to LSP1, LSP14 to LSP16. LSP4 and LSP13 are the positive and negative sense points; LSP2 and LSP15 are the outputs.

PCB artwork

Though the board is pretty compact at 10 by 13 cm, it has room for two large capacitors. I used 35 V 4700 μF caps. The pot is clearly visible at the left center. The opamps I used (AD825) are SMD components. Since my board is single-layer, they are mounted on the bottom side of the board (and thus not visible in the pictures below).

The board displayed here has undergone some minor changes to make it safer. Don't play with mains power unless you know what you're doing, or don't care about your life.

Performance

So see if it was working properly, I connected the regulator to an oldish Tektronix scope with a probe. I measured approximately 10 mV or 0.07% rms noise, with no trace of a 50 Hz signal. I can't say how much of this is actually produced by the regulator, but I'm guessing it's mostly atmospheric noise and the sensitivity of the scope. The probe gave a factor of 10 reduction in the signal, bringing it awfully close to the accuracy of the scope.

Pictures