I'm trying to discover a circuit that will produce a voltage which is some factor of the square root of the input voltage. I.e. \$V_{out}(t) = K\sqrt{V_{in}(t)}\$. The factor K is irrelevant.
I looked at the circuit at the bottom of this page. The problem is it uses a MOSFET and the formula predicting the output requires various parameters \$\mu_n, C_{ox}, V_{th}\$ (some of which I imagine vary greatly even among devices of the same model, and some of which I wouldn't know how to find from the data sheets)
I'd like to find an alternative circuit which has a consistent and predictable output, before I purchase the necessary components.
When I say K is irrelevant, I just meant that I can later amplify the output by a constant factor if needed. It needs to be consistent and predictable though.