The advantage of driving the inverting input
input of the op amp is that the source always sees the resistive
input to ground, provided the amp is operating within its
limits. Driving several sources into an op amp in the
non-inverting configuration will cause each source to see some
of the other sources' signals. So inversion makes mixing much
easier. BUT - now the signal is inverted and if it is to be
otherwise mixed further downstream, re-inverting so that all
signals coming together are of similar phase would be wise.
HTH,
Donald.
On 2021-11-29 11:05 a.m., KI7MWA via
groups.io wrote:
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I've been looking at circuits for audio mixers using op amps.?
Typically, they sum several signals to the op amp's inverting
input, and mention that one can also use the non-inverting input.?
One, in particular, went on to say that if you are planning to
then mix several of these together you probably want to run them
through an amplifier that inverts them again, so that you know
that all your inputs will be in phase.
Or you could just stand on your head!
My question is:? Why not just use the non-inverting input in all
cases, and avoid the whole question of whether the inputs/outputs
are in phase or not?
