[sdiy] CV mixer trouble

[Neil Johnson]

Richie Burnett wrote:
> Don't you just need to adjust the scaling pot PR2 first and locktight
> it, then null out any offset using the PR1 pot?

As long as you have a frequency counter then yes that's work as well.

> I think it may also be a good idea to have a resistor in series with the
> non-inverting input to the op-amp to balance the effects of input bias
> currents.

If the op-amp is a FET type, e.g., TL072, then the bias currents are so 
small as to be worth it (typically 60-100pA).

Cheers
Neil
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