Circuit to calculate square root of voltage?

[Tony Williams]

In article <MPG.1c366e06db5efcb79897fe@130.133.1.4>,
Chaos Master <e-mail@is.INVALID> wrote:

Tony Williams wrote:
Analog Devices Model 433.

Good! Thanks, I will check this circuit and maybe simulate it.

When m=1 the 433 circuit does Vout= X*Y/Z. If Z is
connected back to Vout then X*Y = Vout-squared.
If X is the input and Y is a fixed Vref then it
functions as a square rooter.

However, (AFAIR) Win's suggested AD734 (and say the
B-B MPY600) can function as a direct square-rooter,
without the need for an extra Vref.

This is because this type of multiplier has a high
gain internal opamp, which has X*Y on one input and
Z on the other. Connections are always made so the
the negative feedback forces (X*Y - Z) = 0.

If Z is made the input and Vout connected back to both
X and Y then circuit is forced to do Vout= sq-rt(Z).
No Vref needed.

--
Tony Williams.