When Vgs > Vto and Vds > Vgs - Vto the MOSFET is in the saturation/Active region. In saturation region Id = Kn(Vgs-Vto)^2, so drain current Id is not dependent on Drain-Source voltage Vds.. Here Vto = 1V, 2V <= Vgs <= 4V, Vds = 10V. Green = Vgs,
Blue = Id
