NMOS and PMOS Operating Regions

Equations that govern the operating region of NMOS and PMOS

NMOS:

Vgs < Vt                                     OFF

Vds < Vgs  -Vt                         LINEAR

Vds > Vgs – Vt                        SATURATION

PMOS

Vsg < |Vt|                                 OFF

Vsd < Vsg – |Vt|                    LINEAR

Vsd > Vsg – |Vt|                    SATURATION

Note: 

1.These equations come handy when analyzing any MOS circuit specially to estimate drain current.

2. The negative scale of PMOS curves.