> Firstly, the op-amp doesn't appear to be in
> voltage follower mode

It is.  Note the output tied back to the negative input.

> which is my understanding of a buffer mode.
> Additionally, I'm not sure where any excess voltage is supposed to be
> "disposed" of other than through the op-amp output stage.

This circuit will clamp the top line to the reference voltage plus the
junction drop in the diode.  If the line tries to go above that, current
will flow thru the diode thru the opamp to the negative supply.  This will
work within the opamp's ability to sink the current, which depends on the
opamp.

> Is this okay?

It's OK as long as the opamp can handle the current.  If it can't, you can
add a transistor.  Note also that you could put the diode inside the
feedback loop to clamp more tightly right at the reference voltage.


********************************************************************
Olin Lathrop, embedded systems consultant in Littleton Massachusetts
(978) 742-9014, olin@embedinc.com, http://www.embedinc.com

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