Phase Locked Loop - PLL.

Try a search for 556 PLL. And read through the data sheet that you should be able to locate - it is a PLL IC and should give you some insight into the matter. Better still, look around for any basic electronics book and that should do it.

OK instead of learning what a Mosfet is and using it, you would be better off using a packaged a motor driver as has been suggested by Bruce...

Raghu