An NMOS transistor has parameters \(V_{T O}=0.75 \mathrm{~V}, k_{n}^{\prime}=80 \mu \mathrm{A} / \mathrm{V}^{2}\), \(W / L=15, \phi_{f}=0.37 \mathrm{~V}\), and \(\gamma=0.6 \mathrm{~V}^{1 / 2}\).

(a) The transistor is biased at \(V_{G S}=2.5 \mathrm{~V}, V_{S B}=3 \mathrm{~V}\), and \(V_{D S}=3 \mathrm{~V}\). Determine the drain current \(I_{D}\).

(b) Repeat part (a) for \(V_{D S}=0.25 \mathrm{~V}\).