MOSFET input Voltage for saturation region

[Piyush Gupta]

I'm trying to solve for the minimum v_IN such that MOSFET is in the saturation region. Here are the given parameters
V_S+ = 1.0 V
V_S- = - 1.0 V
V_T = 0.5 V

In order to enter saturation I know that V_DS > V_GS - V_T

V_GS = V_IN - V_S-

V_DS = V_s+ - V_s-, which is 2 V

Which means
2V > V_IN - V_S- - V_T
2V > V_IN - (- 1.0 V) - 0.5 V
2V > V_IN + 0.5 V

I get a V_IN of 1.5 Volts. The correct answer is -0.5 V. I'm just starting to learn electrical engineering and it would be great if someone can point out what's missing.

 

[Piyush Gupta]

I figured it out.
V_GS > V_T
hence
V_IN - V_S- > 0.5 V
V_IN + 1 > 0.5 V
V_IN = -0.5
V_IN can vary from -0.5 to 1.5;