GATE 2022 EC – Question 59
Consider the circuit shown with an ideal long channel $n$MOSFET (enhancement-mode, substrate is connected to the source). The transistor is appropriately biased in the saturation region with $V_{GG}$ and $V_{DD}$ such that it acts as a linear amplifier. $v_i$ is the small-signal ac input voltage. $v_A$ and $v_B$ represent the small-signal voltages at the nodes A and B, respectively. The value of $\frac{v_A}{v_B}$ is ________ (rounded off to one decimal place).
Practise this question in The GATE Grind →
Show answer and explanation
Correct answer: -2
Explanation
The same small-signal current $i_d$ flows through the drain resistor and the source resistor. The drain node A is at $v_A=-i_d\times4\text{k}$ and the source node B at $v_B=i_d\times2\text{k}$, so $\frac{v_A}{v_B}=-\frac{4}{2}=-2.0$.