q for a transistor when vgs -20 v find vdssat if

Question

Q. For a transistor, when v_GS = -2.0 V, find V_DSsat if Vp= -4.0 V for an n-channel depletion mode MOSFET.

Solution:

V_p= -(V_DSsat + v_SG)
but  v_SG = -v_GS = -(-2.0) V
Substituting this in the above equation;

                     -4.0 V = -(V_DSsat + 2.0 V)

ie V_DSsat = 2.0 V

This is the value of v_DS where the pinch-off will occur for the given gate-to-source voltage.