Blars Blarson wrote:

> You're right, I hadn't thought through the turn-on conditions
> properly.  Thanks for having a look.
>
> The darlington specs I looked at tended to have vce(sat) higher that
> simple transistors, but I'm sure you are right about them being better
> than my attempt.


In fairness your approach IS the best way, ie
to drive Q1 base with a constant current ON
level independant of input voltage. Just the
way you configured Q2 regulator wouldn't do what
you wanted.

It's easy enough by adding a 4th transistor,
but if you figure a way to do it without the
extra part that would be great and I don't mind
building and testing it if you come up with a
good solution. :o)
-Roman

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