[sdiy] LM317 LM337 adjustable regulators

[David Ingebretsen]

I am including some on PCB regulation on my Steiner project boards so that
they can run on +-15 or +-12. I decided to use adjustable regulators, the
LM317 and LM337. I wanted to breadboard the circuits to make sure I did the
math right when selecting the trim pot and resistor.

Here's the problem and question. When I turned it on with no load, I could
adjust it fine, but when I put any kind of a load on it, the voltage dropped
by about 10 volts. I was able to trim it back to where I wanted it and when
I tried different loads, the regulator seemed to stay within about 0.1 volts
over a 20:1 load difference.

Is this normal behavior? Does one have to trim the regulator with a load
attached? I don't understand this behavior.

Thanks,

David