power failure

here my mx5 keeps losen power wen im driving,id be driving along next thing the radio goes then the anti lock light comes on and charge and heat.followed by the lights dimming the car slowly loses power and stops. anyone have an idea wat it could be? i reckon it could be the altinater. i asked 1 or 2 people they reckon the same.wats your opinion? all advice welcome.cheers everyone!