hi,
   While reading about common source input  impedance compensation,in text books they are decomposing input impedance as  series combination of -ve R,c in parellel with +ve capacitor.So as to compensate that people are connecting another seris combination of +ve r,c .I understood this very well,but how to get that idea intuitively,means how to came up with decomposing as series combination of _R,_C.can any body please explain this?

Thanks,
Rajasekhar.