AExE01 ยท Chapter 1Basic Electrical & Electronics๐๏ธ Past Licensure QuestionID: 5fa964e3
What is the equation for the drain current of an enhancement NMOS transistor operating in saturation (ignoring channel-length modulation)?
What is the equation for the drain current of an enhancement NMOS transistor operating in saturation (ignoring channel-length modulation)?
Multiple Choice Options
- Aโ Correct Option
Id = K (VGS - VT)^2, with K = (1/2) un Cox (W/L)
- B
Id = K VDS (VGS - VT) - (1/2) K VDS^2
- C
Id = K VGS
- D
Id = 0
Detailed Technical Solution & Explanation
In the saturation region (), the channel pinches off at the drain end. Neglecting channel-length modulation, the drain current of an enhancement-mode NMOS transistor is quadratically related to overdrive voltage: .
Option Analysis:
โข
Option A (^2...): ** Correct. Standard Shockley square-law formulation for saturation mode.
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Option B (- (1/2) K VDS^2): ** Incorrect. Represents the linear (triode) conduction region.
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Option C (Id = K VGS): Incorrect. Conduction is non-linear and requires overcoming threshold voltage .
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Option D (Id = 0): Incorrect. holds only in the sub-threshold cutoff region ().
Reference: Demo2 ยท Set 1NEC Licensure Syllabus