[sdiy] Which opamp pins wiring is best for CV out ?? A , B or C ???

[David G. Dixon]

> What about using "C" but with a 10k resistor in series in the path
> going back to inverting pin to protect from any incoming voltage spikes
> from
> the output connector..?
> Very low output impedance but protected inverting input..
> Best of both world ?
> Again,
> I'm in the CV out design of my sequencer and
> I need so much your thoughts on that.
> Thanks

This reminds me of that old joke where the guy goes to the doctor and says,
"Doc, it hurts when I do this," to which the doctor replies, "Don't do
that."

Yes, A cures oscillation with a capacitive load (by converting the output to
a first-order LPF), and B does not.  However, when does a CV input ever have
a significant input capacitance?  The input capacitance of a typical opamp
is on the level of 10pF, which does not qualify as a capacitive load.

Concerning option C, I can't see that the 10k feedback resistor or the 100pF
capacitor do anything at all separately.  However, together, they convert
the follower into a quadrature oscillator.  This oscillator will be damped
without a (significant) capacitive load, but will oscillate freely with a
capacitive load.  Hence, you definitely don't want to go anywhere near
option C!

Again, I suggest B, or A if you really are feeding a significant capacitive
load, in which case it is probably not a proper CV input anyway, and CV
accuracy doesn't actually matter.