[sdiy] analogue equations

[Tim Stinchcombe]

Hi Ian,

> I was thinking for the math 
> functions: x+y, x-y, x*y, x/y, Sin x, Sin y, Cos x, Cos y, 
> x*x, y*y, square root of x, square root of y. again, if all 
> of these are possible.

If you want to know how to do these in *analog* circuitry, then a good
reference to have would be 'Nonlinear Circuits Handbook: Designing with
analog function modules and ICs', Analog Devices, editor Dan Sheingold, ISBN
091655001X (my copy is 1976, but I dare say other years are possible). There
appear to be several copies at abebooks.com for $10 or so.

It is a little old, and rather higgedly-piggedly (probably just a collection
of application notes flung together), but it does contain many ideas for how
to do division, squares, square roots, approximations to sin & cos etc.
Mostly this is done using polynomial approximations, using lots of
multipliers, summers and fixed gains, so implementing using currently
available chips shouldn't be a real issue (but probably expensive...)

Tim
__________________________________________________________
Tim Stinchcombe 

Cheltenham, Glos, UK
email: tim102 at tstinchcombe.freeserve.co.uk