b. An NMOS transistor has the following values: 𝑉𝑡𝑜 = 1 𝑉, 𝐾𝑃 = 50 𝜇𝐴/𝑉2, 𝐿 = 5 𝜇𝑚, and 𝑊 = 50 𝜇𝑚.

Question

b. An NMOS transistor has the following values: 𝑉𝑡𝑜 = 1 𝑉, 𝐾𝑃 = 50 𝜇𝐴/𝑉2, 𝐿 = 5 𝜇𝑚, and 𝑊 = 50 𝜇𝑚. For each set of voltages, state with reasons the region of operation and compute the drain current.

i. 𝑣𝐺𝑆 = 4 𝑉 and 𝑣𝐷𝑆 = 10 𝑉

ii. 𝑣𝐺𝑆 = 4 𝑉 and 𝑣𝐷𝑆 = 2 𝑉

iii. 𝑣𝐺𝑆 = 0 𝑉 and 𝑣𝐷𝑆 = 10 𝑉

Answer 1

Saturation:

Ohmic:

According to above:

for i., vDS > (vGS - vt) or 10 > 3, thus saturation:

I_D = 0.5*(0.5)(mA/V^2)(4 -1)^2 = 2.25 mA

for ii. vDS > (vGS - vt) or 2 > 3 which is not true, thus Ohmic:

I_D = 0.5(mA/V^2)*((3)(2) - 2)= 2.5 mA

for iii. vGS = 0 (not > = Vt), therefore, the transistor is off and I_D = 0.