Nobody on this forum will design this for you - that is not because people here are stupid, it is because people here are the exact opposite and want to help you to become a good engineer or help solve problems.
If you use Google to search for papers and examples of AGC circuits you will see that there are many resources available to help you.
If you have a specific query about an AGC circuit then thats different ;-)
Don't expect anyone to design this for you - it is a simple task and if you have been asked to do it then you are likely studying engineering and will have already been given the texts to complete it yourself.
If you need one for a 'homer' project - see Google and come back with more specific questions if you get stuck!
Apologies for the rant - please be assured that it is certainly not personal....I just like to rant ;-)
S.