2/4 quadrant multiplier theory

[jorgen.bergfors at idg.se]

>paul perry melbourne australia

>BTW, there is a ckt in Horowitz and Hill 'Art of Electronics'
>that shows how to vary the gain of an op amp stage from 1 to -1,
>with a pot, which I found VERY HANDY for cv inputs..

What is this circuit like? Is it an inverting amplifier with unity gain where 
you connect one end of a pot to the input and the other to the output? The 
wiper then outputs a signal that goes from 1 to -1 gain.
Or is it something more clever?

/Jorgen