[sdiy] Quick CV output buffer query

[Andrew Simper]

Hi Tom,

I'm not an expert so may have this wrong - please chip in guys! It
looks like the output forms a voltage divider to virtual ground, so if
you're not pulling any current at the output you'll get 100k/(100k+1k)
at the output, so if you stick a 100k at the input then this will
cancel out (to within the tolerance of the 100k resistors) since there
will be (100k+1k)/100k gain from the opamp.

Andy

On 13 October 2016 at 19:17, Tom Wiltshire <tom at electricdruid.net> wrote:
> Hi All,
>
> I'm planning a inverting op-amp mixer mixing some CVs in a module. This is then fed to the standard CV output like Olivier has done here (page 2):
>
> http://mutable-instruments.net/static/schematics/Yarns-v03.pdf
>
> If my mixer uses 100K 0.1% resistors, I can be sure what I get out is the same (but upside down) as what I put in. No problem.
>
> How do I arrange that with the output buffer? If I use 100K for the feedback resistor, and 1K for the output protection, do I need a 101K input resistor? How does that work?
>
> Thanks,
> Tom
>
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