Notes on super regulators

[jwb]

I experimented with the Sulzer-type super regulator last night and this morning. My first lesson was the AD797 can be very easily destroyed. I blew away two of these $8 parts immediately. Nevermind that I use a 3M static-free workspace and wrist strap, I blew them up accidentally shorting various pins to various rails. If the positive input is drawing a lot of current, you know you've ruined it.

My second impression is that the Sulzer (and Jung) designs aren't terribly efficient. For every 1W a 14V Sulzer regulator supplies, it dissipates 185mW. A 5V regualtor will dissipate as much power as it provides, or more. The geniuses on this forum probably noticed this right away, but I didn't even give a thought to it until I sat down with the parts and breadboard: this isn't a low-dropout design!

The performance seems excellent. A step from 0 to 400mA load produces no measurable transient at 2mV/div on my scope. Ripple was also unmeasurable with a 1V input ripple and a 400mA load.

To summarize: cheers to Sulzer & Jung, and don't treat your op-amps badly.

PS: This regulator is for my headphone amp, which idles at 200mA current on ± 14V rails per channel.