GATE 2023 IN – Question 56
The nMOS feedback amplifier shown has $\mu_nC_{ox}=1$ mA/V$^2$, threshold $V_T=1$ V, and $W/L=2$. The drain bias voltage is 4 V. Capacitors $C_\infty$ have zero signal-frequency impedance. The gain $V_{out}/V_{in}$ is ______ (two decimal places).
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Show answer and explanation
Correct answer: 0.64 to 0.70
Explanation
The drain current is $I_D=(5-4)/(1\ \mathrm{k}\Omega)=1$ mA. With $\mu_nC_{ox}(W/L)=2$ mA/V$^2$, $g_m=\sqrt{2(2)(1)}=2$ mS. The source-follower gain is $g_mR_S/(1+g_mR_S)=2/3=\boxed{0.67}$.