I don't understand two parts in my text book.
"for a simple common source How can we reduce the input-referred noise voltage? Equation implies that the transconductance of M1 must be maximized. Thus, the transconductance must be maximized if the transistor is to amplify
a voltage signal applied to its gate whereas it must be minimized if the transistor operates
as a constant current source"
Click image for larger version. 

Name:	1.JPG 
Views:	0 
Size:	14.0 KB 
ID:	133445
Why is that??

second problem is if we want to increase the load capacitance of a circuit we should decrease the bandwidth!!