Dual rail adjustable power supply

[Jaguarjoe]

This is just a thought I'm kicking around. Please comment if you would.

I'd take an LM317 suppress the bottom leg below gnd and make a variable 0-15v positive supply. Now take a cheap power op-amp wired as a unity gain inverter and let it follow the positive supply. That should give me an adjustable +/-15v supply. Right?

 

[MikeMl]

A power-op amp usually is not Rail-to-Rail, so you will end up with a lot of unreg power supplys to make it all work.

I vaguely remember a dual-voltage tracking supply was in a collection of app notes published by National?

 

[JimB]

Have a look at this post here on ETO
https://www.electro-tech-online.com/threads/variable-bipolar-power-supply.24291/#post165586
That circuit may do what you require.

JimB

 

[dr pepper]

Interesting circuit, and an interesting idea for powering the 741.
If your gonna use op amps why not use a 78l05 as a reference and use discrete pass transistors for the o/p.
i have a usefull bench supply, it has 2 identical supplys, you can parallel them for 0-30v at 2a, or you can series them for -30-0-30v at 1a tracking, very usefull idea, might have been better if the o/ps were brought out seperately on the from panel though.