Mariss,
Thank you very much for your explanation and I could understand. Because I no experience about MOSFET, so pls help to check the below schematic (CHOPPING.PDF) whether can work well or not?
One more thing I want to ask, last time I use the NON-CHOPPING.PDF to drives the 5Phase pentagon stepper. As your explanation then in this case the P-channel MOSFET will be never turn 'off', but in actually it work well, and P-channel MOSFET get very hot.