Loading effect of op-amps in top-schematic

[reza999]

I formed a top schematic that includes four op-amps. op-amps are designed but in top schematic cascade transistors go to triode and loading effect made some issues. As you can see in pictures two transistors always go to triode in all of op-amps and I couldn't tune them to operate properly.

 

[reza999]

MN7 and MN8 of all op-amps always go to triode

 

[frankrose]

Annotate your operating points and check Vgs of MP6. Maybe the bulk-effect of the PMOS is so high that the Vth is too high.
If it is you can increase the common-mode level of the OPAmps or the better from schematic-design standpoint is if you connect the MP6 bulk to its source.

 

[jjx]

What's VSS tied to? Seems like you have 0 V on the gate inputs. Try and bias to (VDD+VSS)/2 to start with. Don't forget the DC level of the right-most resistor in your picture too (of the four opamps).
As frankrose says, if you annotate the voltages it's easier to see where it fails.