Birth control with antibiotics?

I figured I would post this to get some answers I have strep throat doctors put me on penicillin to get rid of it, but  I was wondering if it really does affect your birth control because my friend was telling me that it made my birthcontrol ineffective I wasn't sure if it was true or not.. Because if I were to have sex I would want my birth control to work. I also wanted to know if it was ineffective how long it would take for them to work again.