GATE EC question library

The general form of the complementary function of a differential equation is given by $y(t)=(A t+B) e^{-2 t}$, where $A$ and $B$ are real constants determined by the initial condition. The corresponding differential equation is

​​​​​In the context of Bode magnitude plots, $40 \mathrm{~dB} /$ decade is the same as $\_\_\_\_\_\_.$

​​​In the feedback control system shown in the figure below $G(s)=\frac{6}{s(s+1)(s+2)}$. $\text{R(s), Y(s)}$, and $\text{E(s)}$ are the Laplace transforms of $r(t), y(t)$, and $e(t)$, respectively. If the input $r(t)$ is a unit step function, then

A digital communication system transmits through a noiseless bandlimited channel $[-W W]$. The received signal $z(t)$ at the output of the receiving filter is given by $z(t)=\sum_{n} b[n] x(t-n T)$ where $b[n]$ are the symbols and $x(t)$ is the overall system response to a single symbol. The received signal is sampled at $t=m T$. The Fourier …

​​​​Consider a lossless transmission line terminated with a short circuit as shown in the figure below. As one moves towards the generator from the load, the normalized impedances $z_{\text{inA }}, z_{i n B}, z_{i n C}$, and $z_{i n D}$ (indicated in the figure) are $\_\_\_\_\_\_.$

​​​Let $\hat{i}$ and $\hat{j}$ be the unit vectors along $x$ and $y$ axes, respectively and let $A$ be a positive constant. Which one of the following statements is true for the vector fields $\overrightarrow{F_{1}}=A(\hat{i} y+\hat{j} x)$ and $\overrightarrow{F_{2}}=A(\hat{i} y-\hat{j} x) ?$ .

​​​​In the circuit below, assume that the long channel $\text{NMOS}$ transistor is biased in saturation. The small signal trans-conductance of the transistor is $g_{m}$. Neglect body effect, channel length modulation and intrinsic device capacitances. The small signal input impedance $Z_{i n}(j \omega)$ is $\_\_\_\_\_\_$

​​​​For the closed loop amplifier circuit shown below, the magnitude of open loop low frequency small signal voltage gain is $40$. All the transistors are biased in saturation. The current source $I_{S S}$ is ideal. Neglect body effect, channel length modulation and intrinsic device capacitances. The closed loop low frequency small signal voltage gain …

​​​​For the Boolean function $$F(A, B, C, D)=\sum m(0,2,5,7,8,10,12,13,14,15) \text{, }$$ the essential prime implicants are $\_\_\_\_\_\_$.

​​​​A white Gaussian noise $w(t)$ with zero mean and power spectral density $\frac{N_{0}}{2}$, when applied to a first-order RC low pass filter produces an output $n(t)$. At a particular time $t=t_{k}$, the variance of the random variable $n\left(t_{k}\right)$ is $\_\_\_\_\_\_\_$.

​​​​A causal and stable $\text{LTI}$ system with impulse response $h(t)$ produces an output $y(t)$ for an input signal $x(t)$. A signal $x(0.5 t)$ is applied to another causal and stable $\text{LTI}$ system with impulse response $h(0.5 t)$. The resulting output is $\_\_\_\_\_\_\_$.

​​​​For non-degenerately doped n-type silicon, which one of the following plots represents the temperature $(T)$ dependence of free electron concentration $(n)$ ?

​In the circuit shown, the $n: 1$ step-down transformer and the diodes are ideal. The diodes have no voltage drop in forward biased condition. If the input voltage (in Volts) is $V_{s}(t)=10 \sin \omega t$ and the average value of load voltage $V_{L}(t)$ (in Volts) is $2.5 / \pi$, the value of $n$ is $\_\_\_\_\_\_\_$.

​​​​​For a causal discrete-time LTI system with transfer function $$H(z)=\frac{2 z^{2}+3}{\left(z+\frac{1}{3}\right)\left(z-\frac{1}{3}\right)}$$ which of the following statements is/are true?

​​​​​Let $\rho(x, y, z, t)$ and $u(x, y, z, t)$ represent density and velocity, respectively, at a point $(x, y, z)$ and time $t$. Assume $\frac{\partial \rho}{\partial t}$ is continuous. Let $V$ be an arbitrary volume in space enclosed by the closed surface $S$ and $\hat{n}$ be the outward unit normal of $S$ Which of the following …

​​​The free electron concentration profile $n(x)$ in a doped semiconductor at equilibrium is shown in the figure, where the points $\mathrm{A}, \mathrm{B}$, and $\mathrm{C}$ mark three different positions. Which of the following statements is/are true?

A machine has a $32$-bit architecture with $1$-word long instructions. It has $24$ registers and supports an instruction set of size $40$. Each instruction has five distinct fields, namely opcode, two source register identifiers, one destination register identifier, and an immediate value. Assuming that the immediate operand is an unsigned integer, …

An amplitude modulator has output (in Volts) $$s(t)=A \cos (400 \pi t)+B \cos (360 \pi t)+B \cos (440 \pi t) .$$ The carrier power normalized to $1 \Omega$ resistance is $50$ Watts. The ratio of the total sideband power to the total power is $1 / 9$. The value of $\text{B}$ (in Volts, rounded off to two decimal places) is $\_\_\_\_\_\_\_$.

In a number system of base $r$, the equation $x^{2}-12 x+37=0$ has $x=8$ as one of its solutions. The value of $r$ is $\_\_\_\_\_\_\_$.

Let $\mathbb{R}$ and $\mathbb{R}^{3}$ denote the set of real numbers and the three dimensional vector space over it, respectively. The value of $\alpha$ for which the set of vectors …