Re: amp question!
This circuit works as a comparator. Consider the branch with Vinp. If Vinp increases, then the current through the PMOS differential pair at that end decreases. Hence, the Vds drop on its active NMOS load decreases. For a moment consider that load to be a resistor because of the rds being modeled as a resistor. When the current is decreasing, then, voltage across the resistor drops. Hence, the PMOS to the left is seeing a lower voltage. Hence the output sees ground. The resistors on the output branches should be weak pull-ups.
Now for the feedback action,since, it is a NMOS transistor, it is taking the output voltage in shunt configuration and feeding it in series to the input branch in the form of current. The NMOS transistor as load actually maintains, the voltage at the node between the differential pair transistor and the output.
I hope that I am clear...............
Added after 1 minutes:
Actually the NMOS transistor size should determine the trip points.........