Interresting topic
Can someone provide mathematical calculation to prove it?
I would extend the question for robust cascode polarization technique below:
![](http://img11.hostingpics.net/pics/428804Sanstitre.jpg)
I know it works fine, but I've never managed to calculate why. I also think that the 2 (or 3, or 4,...) devices at the bottom (that are in triode region) must match the NMOS bias device...
Can someone try to do the calculations? :)