nobody wrote on Aug 30th, 2010, 7:29pm:However, I do not get your point about why M28/M27 are larger.
Therefore it is possible for two biasing legs to have the same swing but it is not that way according the sizes of M27 and M28.
It is in fact possible to make the same swing in both branches, but in that way full swing on the output branch would not be used. In order to fully use the output branch swing, different sizes are required as Analog DE suggested.
nobody wrote on Aug 30th, 2010, 7:29pm:So these two branches are fighting each other. Is that right ?
The answer is no. M23 and M24 set the gate voltage of M27,
but not its current. Such current is set by M15 and M17, which set the
source voltage of M27. Thus the two branches are not fighting each other.
Best
Tosei