Can anyone provide me the amplitude modulator circuit diagram??? Quite urgent !!! Can a common emitter be used as an amp. modulator??

 

That turns out to be a very broad question. Not only are there many ways to do it - http://en.wikipedia.org/wiki/Amplitude_modulation but some methods are better for low power than high.

What is the intended application?

 

If you are wanting a conventional AM broadcast signal I've seen a lot of ways involving simple differential amps. Beenthere is right though, you need to be specific as to application. The term AM also includes suppressed carrier, and/or single side band. Conventional AM (the type used by commercial broadcast stations) is the simplest.

http://www.zen22142.zen.co.uk/spice/ammod.htm

http://www.zen22142.zen.co.uk/Circuits/rf/amtx.htm

http://www.techlib.com/electronics/amxmit.htm

Note: Laws vary according to your location. In the USA power must be limited to no more than 10mw with an antenna 10 feet or less. If you violate your local laws you may find yourself in deep hot water. It may seem like no big deal, but amateur radio types are very jealous of their privileges, and will hunt you down to turn you in, no state monitoring needed. If you don't know the local law don't assume it is OK.