Dear ducvilla
thank you again for your participation
Just want to notify that when you want to simulate the ICMR, there should be no effect from the output. any way if you cconsider your second equation for the NMOS input stage Op-Amp you will see it is above the ground by the value of (Vt1 + Vov1 + Vov5 ), and suppose now if you have replaced t he simple current source with cascod one as in the case of my design, then you will get a worse value...... However if you look to the graph that I showed in the first image, it seem to be that min ICMR is not affected by the cascod connection unless if you take in the account the current source graph as you showed in the first reply of you.
BUT ALSO
go back to the ICMR graph, why the author considered the start of the ICMR range from the moment of the current source (M5) entered the saturation region, it mean he ignored the input transistors saturation condition (Vt1 + Vov1 )???????
Please if you can give me the page Nr. of the ICMR graph
Thank you all once again