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Switch

As in the BJT case (Section 8.3.1), the two extreme operating points Q_max and $Q_{{\rm cutoff}}$ determine the switching action.

The operating point Q_DSS corresponds to the maximum value of I_D, obtained by setting V_GG = 0, since then V_GS=0. Then V_D = V_DD - I_DSSR_D.

The other point $Q_{{\rm cutoff}}$ corresponds to I_D=0, obtained by setting $V_{GG} \geq - V_p$. In this case V_D=V_DD.