I'm assuming you have not been prescribed Adderall or else your doctor would have answered this question for you. Wellbutrin is a very stimulating antidepressant, so it's possible mixing speed with it could make you very anxious or hyper, interfering with your study. Studying on speed isn't a great idea anyway, by the way, it will adversely affect your concentration and memory. It might be useful if you have to finish typing a paper but the best way to study for a test is to study all along so that when tests come up you're pretty much ready; then you can just go over your notes to prepare. Getting enough sleep will serve you better than staying up all night studying. Take it from someone with three college degrees! But if you must do it, then take the advice already given you.