[sdiy] Outputs and Impedances

Youssef Menebhi youssef.menebhi.79 at gmail.com
Fri Oct 26 04:24:33 CEST 2018


And also, do I need discrete buffers for each one of these outputs?
On Thu, Oct 25, 2018 at 10:22 PM Youssef Menebhi
<youssef.menebhi.79 at gmail.com> 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?
> On Thu, Oct 25, 2018 at 10:15 PM <mskala at ansuz.sooke.bc.ca> wrote:
> >
> > On Thu, 25 Oct 2018, Youssef Menebhi wrote:
> > > I have the output of an op-amp in a non-inverting configuration - and
> > > I would like to spread its output to three different inputs.  One
> > > input is a voltage divider feeding into a transformer, the other two
> > > are just voltage dividers.  If I take three equal-sized resistors
> > > (let's say 1k) out of the initial op-amp, will that evenly distribute
> > > the signal? Or do I need additional buffer stages for each output?
> >
> > You shouldn't need the resistors.  Just connect the op amp output to all
> > three inputs in parallel.  "Evenly distributing the signal" shouldn't be
> > an issue; the op amp's output is intended to act as a pure voltage source
> > (very low impedance) and as long as it's able to do that, the presence of
> > other inputs in parallel should not affect the voltage seen by each input.
> >
> > Exceptions would be if the inputs have such low impedances that when
> > connected in parallel they require more current than the op amp can
> > supply; or if there's an issue of interfacing to the outside world, where
> > someone might plug in something weird that screws up both the op amp
> > output and the other inputs.  In those cases, you'd need additional
> > buffering or protective circuitry.
> >
> > --
> > Matthew Skala
> > mskala at ansuz.sooke.bc.ca                 People before tribes.
> > http://ansuz.sooke.bc.ca/


More information about the Synth-diy mailing list