[sdiy] op amp integrators

[Ian Fritz]

Hi Thom --

Your link doesn't work for me, but I'll try to answer.  In your circuit 
there must be a resistor in series with the integrator input.  The 
integration time constant is given by the value of this resistor times the 
value of the cap.  You could use a triple ganged pot to tune all three 
resistors together, or you could use an OTA to feed each integrator.  See 
filter or phasor circuits to see how this is done.  This is the method I am 
using for my present work on VC chaos.

   Ian

At 08:52 AM 10/13/2004, Thom Ash wrote:
>hi everyone.
>
>you might remember a while ago i posted about a module i made that
>generates a Lorenz attractor [www.aovt59.dsl.pipex.com/chaos.html for
>more info/mp3s]. anyway i've been thinking it would be cool to add a
>speed control to it and... well, i need some help :/
>
>the speed of the circuit is determined by the size of the three caps;
>each of these works with an op-amp to form a integrator like this
>['scuse the ascii]...
>
>
>       +----||---+
>       |         |
>       |   |\    |
>dx    | G-|+\___|__ x
>dt ---+---|-/
>           |/
>
>
>i've been told that for a tuned circuit, the time constant is determined
>by a capacitor and a resistor... where would i put a pot to alter the
>speed?
>
>also, the fact that there are three seperate integrations that would
>ideally be controlled by one pot is confusing [to me anyway...] would
>this basically require it to be voltage-controlled and have the pot just
>generate a cv? if so, could someone point me in the right direction?
>
>thanks!
>
>thom