what is strong inversion, below saturation?

[circuitking]

Hi I was reading a paper called "CMOS current reference without resistance by H. Oguey and D. Aebischer". It is said that to keep transistors in 1. weak inversion, saturation 2. Strong inversion, saturation and 3. Strong inversion, below saturation. Could you tell what is the exact differences between these three conditions.

I know
-strong inversion, saturation: Vgs>=Vth and Id follows square law.
-weak inversion is also called subthreshold region and Vgs<Vth.
-weak inversion, saturation : Vgs<Vth and Vds > 4 Vt(Thermal voltage)


No idea what is Strong inversion, below saturation? Is there also weak inversion, linear region? Thanks

 

[dick_freebird]

Strong inversion is really about Vgs/Vgb, establishing
the channel charge sheet robustly. Saturation vs
linear / triode is about the drain pinching or not-yet.
Orthogonal dimensions, or something like.

Weak inversion linear region would just be translated
to the left and down, lower Vgs, lower Vds.