On 31 Dec 2003 14:00:52 -0800, said...
Winfield Hill wrote...

Perhaps my circuit can be combined with Jim's circuit:

: +6.0V, from wall wart
: --+------+------+
: | | |
: | 220 | Q1 2sa1011
: | | |/E pnp TIP32
: 750 +----| etc
: | | |\
: | |/ |
: +----| Q2 |
: | |\E npn |
: | | |
: | +---+--+---- + output
| | to load
__|___/ 2.7k
/ /\ |
/ \--------o
/ \ |
-------- 2.7k
| TL431 |
| |
- ----o----------o------- -

I'm still not happy with the poor dropout-voltage capability of
this circuit. It should be able to operate with Vin much closer
to Vout. Aha! Simply adding a diode and resistor lets us reduce
the dropout voltage down to near the saturation voltage of Q1.

: +5.3 to 9V
: --+-----+------, SIMPLE 5.0V REGULATOR
: | | |
: | 220 | Q1 2sa1011
: | | |/E pnp TIP32
: 470 o----| etc
: | | |\
: | |/ |
: o---| Q2 '----o---- +5.0V
: | |\E npn | output
: | | | to load
: | | 1n4148 |
: | '--o--||---o
| | |
__|___/ 1k 2.7k
/ /\ | |
/ \----- | -------o
/ \ | |
-------- | 2.7k
| TL431 | |
| | |
- ----o--------o--------o---- -

Now, did you do this years ago and just walk through the thought
process for the benefit of the group, kinda like the "Now Read This
Article and Burn it." article, pulling a rabbit out of your hat to
the awe of the crowd? or what?

Happy New Year and best of health.

Mike

Of course, an even more simple circuit is possible, using one
of the many low-cost low-dropout three-terminal regulator ICs.

: +5.3 to 9V etc
: -------, EVEN MORE SIMPLE 5.0V REGULATOR
: __|__
: | |
: | |---+--- +5.0V
: |_____| _|_ output
: | --- to load
: | |
: - -------o------o--- -

But this circuit isn't as much fun. :)

Thanks,
- Win

whill_at_picovolt-dot-com



--
Best Regards,
Mike