Re: slew rate
sreejith,
The important thing to remember is that gain-bandwidth product is a small signal parameter, while slew rate is amplitude dependent. For example, the slew rate of a sine wave with a 10V peak is 10 times the slew rate of a sine wave of the same frequency with a 1V peak. If you attempt to exceed the slew rate capability of an op-amp, one of the intermediate stages of the op-amp will saturate in an attempt to keep up with the input signal slew rate. During this time, the input specifications of the op-amp (input resistance, offset voltage, etc) will not be met. In addition, it will take a long time for the intermediate stage to come out of saturation, especially if the op-amp has a built in frequency compensation capacitor.
Regards,
Kral