The GATE Grind

GATE 2019 EE – Question 26

Analog and Digital Electronics · Amplifiers: biasing, equivalent circuit and frequency response · 1 mark · Multiple choice

Given, $V_{gs}$ is the gate-source voltage, $V_{ds}$ is the drain source voltage, and $V_{th}$ is the threshold voltage of an enhancement type NMOS transistor, the conditions for transistor to be biased in saturation are

  1. $V_{gs}<V_{th};\ V_{ds}\ge V_{gs}-V_{th}$
  2. $V_{gs}>V_{th};\ V_{ds}\ge V_{gs}-V_{th}$
  3. $V_{gs}>V_{th};\ V_{ds}\le V_{gs}-V_{th}$
  4. $V_{gs}<V_{th};\ V_{ds}\le V_{gs}-V_{th}$

Practise this question in The GATE Grind →

Show answer and explanation

Correct answer: (B) $V_{gs}>V_{th};\ V_{ds}\ge V_{gs}-V_{th}$

Explanation

An NMOS transistor conducts when $V_{gs}>V_{th}$ and is in saturation when the channel is pinched off, i.e. $V_{ds}\ge V_{gs}-V_{th}$.