[sdiy] Outputs and Impedances

mskala at ansuz.sooke.bc.ca mskala at ansuz.sooke.bc.ca
Fri Oct 26 05:00:37 CEST 2018

On Thu, 25 Oct 2018, Youssef Menebhi wrote:
> Sorry, but I just need to clarify the exceptions:
> The idea is that the "inputs" that are being fed by the output of the
> single op-amp will serve ultimately as outputs from the device.  So,
> buffers are needed?

If there are voltage dividers between the op amp output and the outside
world, that's probably going to be enough to prevent the outside loads
from affecting each other through the op amp output.  What I was
imagining as a problem would be if you had something like the op amp
output connected *directly* to an output jack, and also to internal
stuff - in that case, someone plugs a short into the output jack and then
no signal gets to the other internal destinations either.

But what are you actually building?  Some sort of interface?  Are you sure
your voltage dividers are going to present the right impedance to the
outside world?  That seems to me more likely to be an issue than the
internal connection between the op amp and the three voltage dividers,
which would normally be just a wire and not require any special design
of its own.

Matthew Skala
mskala at ansuz.sooke.bc.ca                 People before tribes.

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