PWM to V with I feedback

I have an application for a voltage controlled current source to drive a bank of Luxeon high power led's.
I need to use a PWM signal to provide an off to full brightness condition (0 - 2000mA.) I planned on using a simple filter to the non-inverting I/P (+) of an LM351, using the inverting (-) I/P to provide current feedback, and the O/P to drive the gate of a FET.
The current feedback will connect between the source and a .33R resistor.

Will this work? I have to use the LM351 and descrete components, no F to V IC's as this won't give any I feedback.

I'll draw up a schematic and post it shortly.

EDIT: Just found Mel's circuit for the voltage doubler. This idea is similar except supply is 5v and O/P should be from 0 - 5V.