1. Regions of Operation Vg VDD Vds/L = 1V/um Vd Vds = Vgs-Vt Vd VDD VDD
VDD
VDD
Scattering
limited
(OFF)
triode
Sub-Vt
Vtp
(Vgs-Vt )/L= 1V/um
Weak/moderate inversion
Saturation Vg
Saturation Vg
Vtn
Weak/moderate inversion
Scattering
limited
Sub-Vt
triode
(OFF)
VDD Vg Vd Vd
Id=(mnCox)(W/L)(Vgs-Vt-Vds/2) Vds(1+lVds) triode
Id=(mnCox/2)(W/L)(Vgs-Vt)2(1+lVds) saturation
Id=(CoxW/2)(Vgs-Vt)vscl(1+lVds) scattering limited
Id=ISe(Vgs-Vt)/(nVT)(1+Vds/VA) sub-threshold
None of these regions has a hard boundary, and the current varies smoothly from region to region.
Note the symmetry between the NMOS and PMOS devices.