More More 723. Re RE:

The Dark force of dance batzman at gist.net.au
Fri Jan 23 01:51:06 CET 1998


Y-ellow Y'all.
        One more thing that may interest anyone messing with 723s. I notice
that when made adjustable, the 723 is far from linear. That is. If you use a
linear pot as a potential divider replacing R1 and R2 in the circuits given,
you'll find that as the voltage increases over half way, it will suddenly
shoot to the top as the pot is turned.

And out of interest on further investigation, there are two ways to
adjusting the voltage. You can either adjust it through the inverting input
as in Figure 4 or you can put the potential divider across the V-REF amp to
the non-inverting input.

In essence, the 723 provides a buffered Zener and a differential amp. So one
could use a second 723 to provide current sensing I guess. But the thing
that concerns me is that it is Zener referenced through an AMP. And I was
always led to believe that zenners were noisey little buggers. Not ideal for
precision PSUs. Or am I missing something they've done here to minimize the
noise?

Thanks in advance.

Be absolutely Icebox.
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