[sdiy] multiplier from three 741s?

[Paul Perry]

Back in the days before synths even, there were analog computers.. and many 
strange ways were used to multiply voltages.
One way was to take the sum and difference of the two voltages, square the 
voltages (this being easier) and then take the difference.

I think this link shows how to overdrive the 741 output stages to get the 
square function and so on.
http://2005.iccas.org/submission/paper/upload/2multiplier.pdf

I don't expect anyone to use this - but, if you do, I'd like to hear about 
it ;-D

paul perry