[sdiy] analog parabolic EG

[jbv]

Paul Perry a écrit:

> At 10:42 PM 10/08/01 +0000, JB wrote:
> >Could anyone point me to schematics of an
> >analog parabolic evelope generator ?
> >
> Since a parabola is defined by a linear and a squared term,
> you could make a generator from a maximum of 3 multipliers.
>
> paul perry Melbourne Australia



if we consider the basic for of a parabola : y = -(x*x)
1 multiplier and 1 inverter should theorically be enough...

As for the multiplier, the AD633 seems to be a good
candidate... any opinion on that ?

Then we need a linear ramp going from, say, -1V to +1V,
triggered by an external  gate signal. I guess I can get inspiration
by almost any EG schematics.
For different attack & decay times, the ramp would need
to be cut in half : -1 to 0V, and then 0 to +1V.

And being able to voltage control attack & decay times, as well
as amp of the parabola itself would be a nice add-on...

I'm sure I could achieve something by myself, but due to
lack of time, I was wondering whether some schemo would
be already available somewhere...

JB