Solution 2:

(a)

KO = K'(W / L)O = 20 * (20 / 2) = 200 * 10^-6 A / V^2

KL = K'(W / L)L = 20 * (10 / 5) = 40 * 10^-6 A / V^2

(b)

The input high voltage = 4v

Hence both the transistors are in the linear region of operation.

Therefore,

I(DL) = I(DO)

KL [(Vgs - Vt)Vds - Vds^2 / 2] = KO [(Vgs - Vt)Vds - Vds^2 / 2]

40 [(7 - Vo - 1 )*(5 - Vo) - (5 - Vo)^2 / 2] = 200 [(4 -1)Vo - Vo^2 / 2]

Vo^2 - 21Vo + 17.5 = 0

Vo = 0.87v

Hence the output voltage, Vout = 0.87v