Ritesh, you really don't get it, do you?
If you want help, you've got to give us something to work with. Sure, we could just post links to lots of audio amp circuits. But you said you want to design one.
That means YOU get do design it. You. Understand?
In other words, show some initiative. Have you sketched any designs? even a messy scrawl on the back of an envelope. Anything to show us that you're serious about trying to learn, and not just wanting us to spoon-feed you.
Any ideas at all about your 5 to 7-watt audio amp?
We'll be happy to help you IF you give us a sign that you're serious. Otherwise, people like the last respondent are going to think you're just a troll, and one with lousy language skills at that. (It wouldn't hurt to try to improve your English as well, since that's the language we're using here. If I were posting on a board in your country using your native language, I would expect to get laughed at if I couldn't put together an understandable sentence. Same thing here.)
See how this works?