The GATE Grind

GATE 2016 EC – Question 28

Analog Circuits · BJT and MOSFET Amplifiers · 1 mark · Multiple choice

What is the voltage $V_{out}$ in the following circuit?

A CMOS inverter made of a PMOS transistor from $V_{DD}$ and an NMOS transistor to ground, with the common gate input connected to the output $V_{out}$ through a 10 kΩ resistor.
  1. 0 V
  2. $(|V_T \text{ of PMOS}| + V_T \text{ of NMOS}) / 2$
  3. Switching threshold of inverter
  4. $V_{DD}$

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Correct answer: (C) Switching threshold of inverter

Explanation

The gates draw no current, so there is no voltage drop across the 10 kΩ resistor, and the gate voltage equals the output voltage. The inverter then sits at the point where its input and output are equal, which is its switching threshold.