I had a bad boss once. Oh, she was the worst! She blamed me for the entire team's low moral even though I was on the first floor and the rest of the team was stationed on the 2nd. If anything did go wrong, then it was somehow my fault or I did something to cause someone to do it wrong. Just the worst ever! I pray that you don't have a bad boss, but if you do, there are some ways to deal with the situation.
Step 1: Establish transparent communication. Your first line of communication should be to talk to your boss directly. Following the meeting, send a quick email to "memorialize the substance of your conversation."
Step 2: Work to the best of your ability. Bad bosses sabotage your best efforts and confidence, which makes it easy to call you out as an underperformer, but if you complete your tasks to the best of your ability, you'll have a stronger foundation to stand (and defend yourself) on.
Step 3: Separate yourself from the situation, but don't become isolated. While you might not have the power to, say, fire your supervisor, it can help to remember that they only control your actions during the hours that you're working.
Step 4: Move up or move on.