Here it is. The input op amp gives a about 10 to 1 voltage gain. The dual op amp does the rectifying and RMS conversion. That is straight out of the old National Semiconductor op amp circuit collection. If the output changes too slowly, decrease the size of C1, but don't go below 1 microfarad, or you'll see ripple. The R1 trimmer will let you scale the output to 3 volts for 333 mv in.

Do you still have the image of the circuit?

Or does anyone know if there is an IC that can take care of this?

 

Actually, we encourage new posts, and discourage hijacking old threads, as it can be confusing. This is the old thread - http://forum.allaboutcircuits.com/showthread.php?t=7792.

At this remove, it might be nice if you could state what your interest is in terms of the signal and so on.

As far as the RMS conversion goes, there are several IC's that do the conversion, if that's what you mean.