Question

For a MOSFET, the pinch-off voltage is -3V. Gate to source voltage is 20V. W/L ratio is 5. Process transconductance parameter is 40μA/V^2. Find drain to source current in saturation.

(a) 0.10 mA

(b) 0.05mA

(c) – 0.05mA

(d) – 50A

I got this question at a job interview.

My enquiry is from Biasing of JFET and MOSFET topic in portion FET Amplifiers of Analog Circuits

Answer 1

The correct answer is (c) – 0.05mA

For explanation I would say: ISD = k’W(VSG – |VT|)^2/2L

ISD = 20*5*(-20-3)^2 = 52900μA = 0.05mA.