[sdiy] Best way to limit control voltage

[harrybissell]

schematic ???   :^P

I'm not sure I understood.  you have MANY inputs, and you want ONE
of them to be unrestricted (lets say goes to +10V) but you want the
sum of the other voltages never to exceed (lets say) 5V.

If you can stand the change in input impedance, you could zener of actively
limit each input.  When it clamps, the input impedance will drop (perhaps
a lot)

You could clamp after summing, and just let the one input bypass the clamp
stage.

If you don't need super precision, I'd go with a zener clamp in the feedback of
the summing amp, and bypass the full range input to a second summing amp.

H^) harry

"J. Larry Hendry" wrote:

> I'd like to tap into the vast expertise again and ask what methods people
> are using to be efficient with limiting a control voltage.  I am designing a
> circuit that will have more than one input.  One of the inputs needs to be
> capable of producing the full output range needed in the circuit.  But, I
> also want to limit (or clamp) the output so it does not exceed my
> predetermined values.  The sum of the inputs might normally cause that to
> happen.  I cannot solve this with scaling.  So, I need to consider efficient
> ways to clamp the output to within a certain range.  I have an idea that
> will work.  But, it is not as part efficient as I would like to be.  So, I
> would appreciate hearing from others about their approach to this issue.
>
> Thanks
> Larry Hendry