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GATE 2014 EC (EC2) – Question 48

Electronic Devices · P-N Junction and Semiconductor Devices · 2 marks · Multiple choice

The NMOS shown has threshold 0.8 V. Ignore channel length modulation. At drain voltage V_D = 1.6 V, I_D = 0.5 mA. Adjust R and V_DD to obtain V_D = 2 V. Find new I_D (mA).

Diagram for GATE 2014 EC (EC2) question 48
  1. 0.625
  2. 0.75
  3. 1.125
  4. 1.5

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Show answer and explanation

Correct answer: (C) 1.125

Explanation

Gate and drain are tied, so VGS=VDS and the device is saturated whenever on. Ignoring channel-length modulation, ID is proportional to(VGS−VT)². The overdrive changes from1.6−0.8=0.8V to2−0.8=1.2V. Thus ID,new=0.5×(1.2/0.8)²=**1.125mA,C**.