The merlin project. :)

[The Dark force of dance]

Y-ellow Ladies and diodes.
        let me point out first that I live in a technological desert. I've
had trouble getting 100K resistors here in the past. let alone any of this
hoopy, new fan dangled modern stuff. If I could just rush out and buy a more
appropriate solution off the shelf I would most certainly do so. But as it
is, I have to make do with what I can scrounge up. Which in this case
happens to be 723s.

At 11:08 AM 2/7/98 -0500, Tony Clark wrote:

>   How exactly do you plan to get 3V out when your battery is down to 
>that level?  Now utilizing an LM4040 buffered through an op-amp will 
>allow you to get down to less than 4V before the reference starts losing 
>it and that's pretty good if you ask me.

What I did find was an LM336. Which is a 2.5 volt reference diode. A similar
type of thing to the 4040 except it has an adjustment pin. I looked round
and found a bunch of programmable op-amps. LM4250s. Which will operate down
to 2 volts. Essentially what I found was that I can get it to operate down
to just about 4 volts before it drops out. That's with about 800ohms onto
the reference. Which @ 12 volts draws 14ma. @ 3 it's only 6ma. But when I
use the reference for both regulators, I get a drift of about 200milivolts.
I think this is due to changing voltage on the programming pin of the 4250.
Strange things happen with this reference and op-amp but Tony's point about
drop out vs current consumption is well taken.

I don't want to use a second reference and op-amp as I'm running out of
board space as it is. But I have a couple of other trix to try out. Unless
Paul P comes up with a couple of these 3 volt regs he was talking about.
Which would save me a hell of a lot of board space I guess. :) But I
certainly can't get them down here. Last time I tried, I couldn't even get a
zener below 5.1 volts. The kid in the shop tried to tell me that they
couldn't make zeners lower than that. He suggested that it was physically
impossible. Yea right!

Thanks for all the suggestions so far. I don't know what I'd do without you
guys. I'll keep at it.

Be absolutely Icebox.
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