In the circuit, $I_{\mathrm{DC}}$ is an ideal current source. The transistors $M_1$ and $M_2$ are assumed to be biased in saturation, wherein $V_{\text {in }}$ is the input signal and $V_{D C}$ is fixed DC voltage. Both transistors have a small signal resistance of $r_{d s}$ and trans-conductance of $g_m$. The small signal output impedance of this circuit is

In the circuit, shown below, if the values of $R$ and $C$ are very large, the form of the output voltage for a very high frequency square wave input, is best represented by

The op-amps in the following circuit are ideal. The voltage gain of the circuit is ___________. (Round off to the nearest integer)

Selected data points of the step response of a stable first-order linear time-invariant (LTI) system are given below. The closest value of the time-constant, in sec, of the system is

$$ \begin{array}{|l|c|c|c|c|c|} \hline \text { Time (sec) } & 0.6 & 1.6 & 2.6 & 10 & \infty \\ \hline \text { Output } & 0.78 & 1.65 & 2.18 & 2.98 & 3 \\ \hline \end{array} $$