I think the Google Adsense help pages would be a good start for you: https://www.google.com/adsense/support/
Do you mean a limit to how much you can earn? If so, the answer is a simple no. The more traffic you have, the higher the likely CTR, the higher the likely earnings. The amount earned by people ranges from a few cents to publishers that are earning $10,000 or more a month.