On the other side of the coin from sampling, do you ever use any kind of reconstruction filter in a control loop? I have never, ever done so; if I'm concerned about the edges of my drive samples it means I'm sampling too slow and I need to correct the problem. The only time that I could see doing it would be if I were driving some otherwise well-behaved plant that were somehow sensitive, but that seems to be a rare thing.
------------------------------------------- Tim Wescott Wescott Design Services