Re: Need help with a circuit

From: Bob (nimby1_notspamm__at_earthlink.net)
Date: 12/28/04 

Date: Tue, 28 Dec 2004 16:02:02 GMT

"Dark Alchemist" <GhostOfACPast@gmail.com> wrote in message
news:1104247897.145478.267140@f14g2000cwb.googlegroups.com...
> I need a circuit that can perform the following
>
> if (x < -1)
> x = 0
> else if (x < 1)
> x = sqrt(1 - (x^2))
> else
> x = 0
>
> Now what I have done so far is the comparisons and have three
> comparators so at a given x the appropiate values are given (1, -1, 0).
> I have taken care of the square root, minus, and the square part as
> well.
>
> So, does anyone know what I use and how to do the if then else parts?
> 3 outputs and only one is needed at the input to the rest of the
> circuit. I don't want a specialized ic for this so its just or, not,
> and, xor, etc...
>
> Thank you. :)
>

It seems like your equations should use a different variable name for the
output of the function. For example:
 if (x<-1)
    y=0
...
...
where x is the input and y is the output, right?

Also, if you look at your possible values for x then you'll see what the
"else" part really is. You're on the right track by realizing that you need
comparitors. Now, you just need to write out the truth table (for the
comparitor outputs as the input to your logic function) and then just reduce
the logic to drive your math (zero or sqrt(1-x^2)) function.

Bob

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