type mosfet using for control motor stepper
If you want to go discrete, you have to build something like this...X5. For higher speeds it gets more complicated. Opto on input is not mandatory, but it is good idea to avoid problems and protect your computer. Values are calculated based on motor data, power supply and used parts. This is just to get you idea of what you can avoid if you go integrated. Factory driver board is usually best and most cost effective solution, there is no need to re-invent the wheel.