Hi Chandrakant,
I know you mentioned on your earlier post that you were applying a pulsed input with a varied duty cycle. Other than a sine or pulsed input, have you tried applying a square, triangle, or saw-tooth wave input with variable frequency and duty cycle? Also, make sure that the DC offset of the generator you are using is not introducing any DC offset to your generated signal. Some oscilloscope output plots would be really helpful in allowing us to see what exactly is going on with the circuitry.
Thanks,
Joe