Question

For an n-channel MOSFET, if conduction parameter (k_n) is 0.249 mA/V², gate to source voltage V_QS is 2V_TN where V_TN = 0.75V. The current will be
1. 0.160 mA
2. 0.150 mA
3. 0.140 mA
4. 0.170 mA

Answer 1

Correct Answer - Option 3 : 0.140 mA

Concept:

For an n-channel MOSFET, the current in triode and saturation region is given by:

ID = Kn [2VDS(VGS - Vth) - VDS2)]  when VDS < VGS - Vth

\(I_D=K_n(V_{GS}-V_{th})^2\) when VDS > VGS - Vth

VDS = Drain to Source Voltage

VGS = Gate to source voltage

Vth = Threshold Voltage

Kn = Conduction parameter

Analysis:

Given: Kn = 0.249 mA / V2

VGS = 2VTN

VTN = 0.75 V

∵ VGS – VTN = 0.75 V

And VDS is usually more than that

∴ VDS > VGS - VTN

And the MOSFET is in saturation.

I_D = 0.249 (2V_TN - V_TN)²

= 0.249 (V_TN)²

= 0.249 (0.75)²

= 0.14 mA