[sdiy] Analog Computational Unit

[Ingo Debus]

Am Sonntag, 01.02.04 um 04:32 Uhr schrieb James Patchell:

> I was also thinking of doing a module that would produce:
>
> Y = +/-Ax^3 +/-Bx^2 +/- Cx
>
> It can be easily done using three AD633, a summer and three opamps set 
> up as an adjustable attenuator with both positive and negative gain (I 
> use a similar circuit in my diode shaper)....
>

Why three? If you want x^3 and x^2, can't you just use two, one to get 
x^2 from x, and another one to get x^3 from x^2 (i.e. output of the 
first AD633) and x?

Or are A, B and C control voltages? In this case I don't see why you 
need *only* three.

Ingo