Thanks for the response. I've used a transistor and a MOSFET as a driver. i've tested the circult, it's only drawing 0.4mA from the controller. I've changed my inverter to a CMOS hex inverter; it seems to be working fine now. But I still haven't decided what frequency I should drive my motor with. Is there a formula that I can use to work it out using it's time constant or raise time?

thanks again

jzl