Previous Year Questions
4 papers · 181 questions — organised by subject with solutions and explanations.
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Two silicon diodes, with a forward voltage drop of 0.7 V, are used in the circuit shown in the figure. The range of input voltage for which the output voltage , is
In the differential amplifier shown in the figure, the magnitudes of the commonmode and differential-mode gains are , respectively. If the resistance is increased, then
A good current buffer has
In the ac equivalent circuit shown in the figure, if is the input current and is very larger, the type of feedback is
In the low-pass filter shown in the figure, for a cut-off frequency of 5 kHz, the value of (in K ) is _____.
Assuming that the Op-amp in the circuit shown is ideal, is given by
A cascade connection of two voltage amplifiers A1 and A2 is shown in the figure. The open-loop gain , input resistance and output resistance for A1 and A2 are as follows : The approximate overall volt
The figure shows a half-wave rectifier. The diode D is ideal. The average steady-state current (in Amperes) through the diode is approximately_____.
For the n-channel MOS transistor shown in the figure, the threshold voltage is 0.8 V. Neglect channel length modulation effects. When the drain voltage = 1.6 V, the drain current was found to be 0.5 m
In the circuit shown, the silicon BJT has . . Which one of the following statements is correct ?
For the MOSFETs shown in the figure, the threshold voltage = 2 V and . The value of (in mA) is ____.
An increase in the base recombination of a BJT will increase
If the emitter resistance in a common-emitter voltage amplifier is not bypassed, it will
A BJT in a common-base configuration is used to amplify a signal received by a 50 antenna. Assume kT/q = 25mV. The value of the collector bias current (in mA) required to match the input impedance of
For the amplifier shown in the figure, the BJT parameters are , and thermal voltage . The voltage gain of the amplifier is ____.
In the circuit shown, the op-amp has finite input impedance, infinite voltage gain and zero input offset voltage. The output voltage is
The circuit shown represents
For the MOSFET shown in the figure, assume W/L=2, =2.0 V, and . The transistor switches from saturation region to linear region when (inVolts) is ____.
For the common collector amplifier shown in the figure, the BJT has high , negligible , and = 0.7 V. The maximum undistorted peak to peak output voltage (in Volts) is _____.
The feedback topology in the amplifier circuit ( the base bias circuit is not shown for simplicity) in the figure is
The diode in the circuit shown has = 0.7 Volts but is ideal otherwise. If Volts, the minimum and maximum values of (in Volts) are, respectively,
The desirable characteristics of a transconductance amplifier are
In the circuit shown, the PNP transistor has . Assume that . For to be 5 V, the value of (in ) is ____.
Consider the common-collector amplifier in the figure (bias circuitry ensures that the transistor operates in forward active region, but has been omitted forsimplicity). Let be the collector current,
In the voltage regulator circuit shown in the figure, the op-amp is ideal. The BJT has and , and the zener voltage is 4.7 V. For a regulated output of 9V, the value of R (in ) is _____.
In the figure, assume that the forward voltage drops of the PN diode and Schottky diode are 0.7 V and 0.3 V, respectively. If ON denotes conducting state of the diode and OFF denotes non-conducting st
Let X be a real-valued random variable with E[X] and denoting the mean values of X and , respectively. The relation which always holds true is
In a double side-band (DSB) full carrier AM transmission system, if the modulation index is doubled, then the ratio of total sideband power to the carrier power increases by a factor of ______.
A fair coin is tossed repeatedly until a 'Head' appears for the first time. Let L be the number of tosses to get this first ' Head' . The entropy H (L) in bits is _____.
The input to a 1-bit quantizer is a random variable X with pdf for and for . For outputs to be of equal probability, the quantizer threshold should be ____.
The capacity of a band-limited additive white Gaussian noise (AWGN) channel is given by bits per second (bps), where W is the channel bandwidth, P is the average power received and is the one sided po
A real band-limited random process X(t) has two sided power spectral density where is the frequency expressed in Hz. The signal X(t) modulates a carrier and the resultant signal is passed through an i
Let , , and be independent and identically distributed random variables with the uniform distribution on [0,1]. The probability is___.
Consider a communication scheme where the binary valued signal X satisfies P{X =+1} = 0.75 and P{X =-1} = 0.25. The received signal Y = X + Z , where Z is a Gaussian random variable with zero mean and
Consider sinusoidal modulation in an AM system. Assuming no overmodulation, the modulation index ( ) when the maximum and minimum values of the envelope, respectively, are 3 V and 1 V, is ______.
A binary random variable X takes the value of 1 with probability 1/3. X is input to a cascade of 2 independent identical binary symmetric channels (BSCs) each with crossover probability 1/2. The outpu
Let X(t) be a wide sense stationary (WSS) random process with power spectral density . If Y(t) is the process defined as Y(t)=X(2t-1), the power spectral density is
Consider an FM signal . The maximum deviation of instantaneous frequency from the carrier frequency is
A modulated signal is , where the baseband signal m(t) has frequency components less than 5 kHz only. The minimum required rate (in kHz) at which y(t) should be sampled to recover m(t) is _____.
If the figure, M(f) is the Fourier transform of the message signal m(t) where A = 100 Hz and B = 40 Hz. Given and , where . The cutoff frequencies of both the filters are . The bandwidth of the signal
Consider the Z-channel given in the figure. The input is 0 or 1 with equal probability. If the output is 0, the probability that the input is also 0 equals ____
Let be the BER of a BPSK system over an AWGN channel with twosided noise power spectral density . The parameter is a function of bit energy and noise power spectral density. A system with two independ
The capacity of a Binary Symmetric Channel (BSC) with cross-over probability 0.5 is _____.
Consider a random process , where the random phase is uniformly distributed in the interval . The auto-correlation is
In a PCM system, the signal V is sampled at the Nyquist rate. The samples are processed by a uniform quantizer with step size 0.75 V. The minimum data rate of the PCM system in bits per second is ____
An M-level PSK modulation scheme is used to transmit independent binary digits over a band-pass channel with bandwidth 100 kHZ. The bit rate is 200 kbps and the system characteristic is a raised-cosin
In a code-division multiple access (CDMA) system with N = 8 chips, the maximum number of users who can be assigned mutually orthogonal signature sequences is____.
Let X be a zero mean unit variance Gaussian random variable. E[|X|] is equal to ______.
The power spectral density of a real stationary random process X(t) is given by The value of the expectation is _____.
An analog voltage in the range 0 to 8 V is divided in 16 equal intervals for conversion to 4-bit digital output. The maximum quantization error (in V) is_____.
Let be independent and identically distributed random variables with the uniform distribution on [0,1]. The probability P{ is the largest} is
Consider a discrete-time channel Y = X + Z , where the additive noise Z is signaldependent. In particular, given the transmitted symbol , at any instant, the noise sample Z is chosen independently fro
Coherent orthogonal binary FSK modulation is used to transmit two equiprobable symbol waveforms and [/latex] S_{2}(t)= cos 2 f_{2}t[/latex] , where = 4 mV. Assume an AWGN channel with two sided noise
Consider the feedback system shown in the figure. The Nyquist plot of G(s) is also shown. Which one of the following conclusions is correct ?
The steady state error of the system shown in the figure for a unit step input is _____.
Consider the state space model of a system, as given below The system is
In the root locus plot shown in the figure, the pole/zero marks and the arrows have been removed. Which one of the following transfer functions has this root locus ?
For the following feedback system . The 2% settling time of the step response is required to be less than 2 seconds. Which one of the following compensators C(s) achieves this ?
For the second order closed-loop system shown in the figure, the natural frequency (in rad/s) is
Consider the state space system expressed by the signal flow diagram shown in the figure. The corresponding system is
The state equation of a second-order linear system is given by For and for when , x(t) is
The forward path transfer function of a unity negative feedback system is given by The value of K which will place both the poles of the closed-loop system at the same location, is ______.
The Bode asymptotic magnitude plot of a minimum phase system is shown in the figure If the system is connected in a unity negative feedback configuration, the steady state error of the closed loop sys
The natural frequency of an undamped second-order system is 40 rad/s. If the system is damped with a damping ratio 0.3, the damped natural frequency in rad/s is ______.
An unforced linear time invariant (LTI) system is represented by If the initial conditions are , the solution of the state equation is
The phase margin in degrees of calculated using the asymptotic Bode plot is _____.
The characteristic equation of a unity negative feedback system is . The open loop transfer function G(s) has one pole at 0 and two poles at -1. The root locus of the system for varying K is shown in
In a Bode magnitude plot, which one of the following slopes would be exhibited at high frequencies by a order all-pole system ?
For the following system, when , the transfer function is
The state transition matrix of a system is
Consider a transfer function with a positive real parameter. The maximum value of until which remains stable is ____.
Consider the following block diagram in the figure. The transfer function is
In the circuit shown in the figure, if C = 0, the expression for Y is
In the circuit shown, W and Y are MSBs of the control inputs. The output F is given by
The output F in the digital logic circuit shown in the figure is
For an n-variable Boolean function, the maximum number of prime implicants is
The circuit shown in the figure is a
An 8-to-1 multiplexer is used to implement a logical function Y as shown in the figure. The output Y is given by
Consider the Boolean function, . Which one of the following is the complete set of essential prime implicants ?
The digital logic shown in the figure satisfies the given state diagram when is connected to input A of the XOR gate. Suppose the XOR gate is replaced by an XNOR gate. Which one of the following optio
If WL is the Word Line and BL the Bit Line, an SRAM cell is shown in
Consider the multiplexer based logic circuit shown in the figure. Which one of the following Boolean functions is realized by the circuit ?
In the following circuit employing pass transistor logic, all NMOS transistors are identical with a threshold voltage of 1V. Ignoring the body-effect, the output voltages at P, Q and R are,
Five JK flip-flops are cascaded to form the circuit shown in Figure. Clock pulses at a frequency of 1MHz are applied as shown. The frequency (in kHz) of the waveform at Q3 is______
In a half-subtractor circuit with X and Y as inputs, the Borrow (M) and Difference (N=X-Y) are given by
The outputs of the two flip-flops Q1, Q2 in the figure shown are initialized to 0, 0. The sequence generated at Q1 upon application of clock signal is
In the circuit shown, choose the correct timing diagram of the output (y) from the given waveforms W1, W2, W3 and W4.
The Boolean expression simplifies to
The number of bytes required to represent the decimal number 1856357 in packed BCD (Binary Coded Decimal) form is_______.
If X and Y are inputs and the Difference (D=X-Y) and the Borrow (B) are the outputs, which one of the following diagrams implements a half-subtractor ?
The output (Y ) of the circuit shown in the figure is
A 16-bit ripple carry adder is realized using 16 identical full adders (FA) as shown in the figure. The carry-propagation delay of each FA is 12 ns and the sumpropagation delay of each FA is 15 ns. Th
For a parallel plate transmission line, let v be the speed of propagation and Z be the characteristic impedance. Neglecting fringe effects, a reduction of the spacing between the plates by a factor of
The force on a point charge kept at a distance d from the surface of an infinite grounded metal plate in a medium of permittivity is
In the following figure, the transmitter sends a wideband modulated RF signal via a coaxial cable to the receiver . The output impedance of , the characteristic impedance of the cable and the input im
Consider an air filled rectangular waveguide with a cross-section of 5cm x 3cm. For this waveguide, the cut-off frequency (in MHz) of mode is ____.
Assume that a plane wave in air with an electric field is incident on a non-magnetic dielectric slab of relative permittivity 3 which covers the region . The angle of transmission in the dielectric sl
Which one of the following field patterns represents a TEM wave travelling in the positive x direction ?
For a rectangular waveguide of internal dimensions , the cur-off frequency for the mode is the arithmetic mean of the cut-off frequencies for mode and mode. If a = cm, the value of b (in cm) is______.
A two-port network has scattering parameters given by . If the port-2 of the two port is short circuited, the parameter for the resultant one port network is
In the transmission line shown, the impedance (in ohms) between node A and the ground is _____.
If is the electric field in a source free region, a valid expression for the electrostatic potential is
The electric field (assumed to be one-dimensional) between two points A and B is shown. Let and be the electrostatic potentials at A and B, respectively. The value of in Volts is
The input impedance of a section of a lossless transmission line of characteristic impedance 50 is found to be real when the other end is terminated by a load . If X is 30 , the value of R(in ) is____
To maximize power transfer, a lossless transmission line is to be matched to a resistive load impedance via a transformer as shown. The characteristic impedance (in ) of the transformer is ___
If the electric field of a plane wave is - (mV/m), the polarization state of the plane wave is
A region shown below contains a perfect conducting half-space and air. The surface current on the surface of the perfect conductor is amperes per meter. The tangential field in the air just above the
The cut-off wavelength (in m) of light that can be used for intrinsic excitation of a semiconductor material of bandgap = 1.1 eV is _____.
In the figure, ) is plotted as a function of 1/T , where is the intrinsic resistivity of silicon, T is the temperature, and the plot is almost linear. The slope of the line can be used to estimate
At T = 300 K, the band gap and the intrinsic carrier concentration of GaAs are 1.42 eV and , respectively. In order to generate electron hole pairs in GaAs, which one of the wavelength ranges of incid
A thin P-type silicon sample is uniformly illuminated with light which generates excess carriers. The recombination rate is directly proportional to
In MOSFET fabrication, the channel length is defined during the process of
The slope of the vs. curve of an n-channel MOSFET in linear regime is at = 0.1V. For the same device, neglecting channel length modulation, the slope of the vs. curve (in ) under saturation regime is
When the optical power incident on a photodiode is 10 W and the responsivity is 0.8 A/W, the photocurrent generated (in A) is _____.
An N -type semiconductor having uniform doping is biased as shown in the figure. If is the lowest energy level of the conduction band, is the highest energy level of the valance band and is the Fermi
In CMOS technology, shallow P-well or N -well regions can be formed using
The donor and accepter impurities in an abrupt junction silicon diode are and , respectively. Assume that the intrinsic carrier concentration in silicon at 300K, and the permittivity of silicon . The
A silicon bar is doped with donor impurities . Given the intrinsic carrier concentration of silicon at T = 300 K is . Assuming complete impurity ionization, the equilibrium election and hole concentra
Consider two BJTs biased at the same collector current with area and . Assuming that all other device parameters are identical, kT/q = 26 mV, the intrinsic carrier concentration is and , the differenc
A BJT is biased in forward active mode. Assume = 0.7 V, kT/q = 25mV and reverse saturation current . The transconductance of the BJT (in mA/V) is _____.
An ideal MOS capacitor has boron doping-concentration of in the substrate. When a gate voltage is applied, a depletion region of width 0.5 m is formed with a surface (channel) potential of 0.2 V. Give
Assume electronic charge , kT/q=25mV and electron mobility . If the concentration gradient of electrons injected into a P-type silicon sample is , the magnitude of electron diffusion current density (
If fixed positive charges are present in the gate oxide of an n-channel enhancement type MOSFET, it will lead to
A depletion type N-channel MOSFET is biased in its linear region for use as a voltage controlled resistor. Assume threshold voltage , , and . The value of the resistance of the voltage controlled resi
Consider a silicon sample doped with donor atoms. Assume that the intrinsic carrier concentration . If the sample is additionally doped with acceptor atoms, the approximate number of electrons/ in the
Consider an abrupt PN junction (at T = 300 K) shown in the figure. The depletion region width on the N -side of the junction is 0.2 m and the permittivity of silicon ( ) is F/cm. At the junction, the
At T = 300 K, the hole mobility of a semiconductor and . The hole diffusion constant is _____.
When a silicon diode having a doping concentration of on p -side and on n-side is reverse biased, the total depletion width is found to be 3 m. Given that the permittivity of silicon is F/cm, the depl
The doping concentrations on the p-side and n-side of a silicon diode are and , respectively. A forward bias of 0.3 V is applied to the diode. At T=300K, the intrinsic carrier concentration of silicon
An 8085 microprocessor executes "STA 1234H" with starting address location 1FFEH (STA copies the contents of the Accumulator to the 16-bit address location). While the instruction is fetched and execu
For the 8085 microprocessor, the interfacing circuit to input 8-bit digital data h from an external device is shown in the figure. The instruction for correct data transfer is
In the circuit shown in the figure, the angular frequency (in rad/s), at which the Norton equivalent impedance as seen from terminals is purely resistive, is _____.
Norton's theorem states that a complex network connected to a load can be replaced with an equivalent impedance
In the circuit shown in the figure, the value of node voltage is
The magnitude of current (in mA) through the resistor in the figure shown is______.
In the figure shown, the value of the current I (in Amperes) is_____.
In the h-parameter model of the 2-port network given in the figure shown, the value of (in S ) in _____.
A periodic variable x is shown in the figure as a function of time. The root-mean-square (rms) value of x is _____.
A Y-network has resistances of 10 each in two of its arms, while the third arm has a resistance of 11 . In the equivalent -network, the lowest value (in ) among the three resistances is _____.
In the circuit shown in the figure, the value of capacitor C (in mF) needed to have critically damped response i(t) is _____.
A 230 V rms source supplies power to two loads connected in parallel. The first load draws 10 kW at 0.8 leading power factor and the second one draws 10 kVA at 0.8 lagging power factor. The complex po
The equivalent resistance in the infinite ladder network shown in the figure is . The value of /R is ____.
In the figure shown, the capacitor is initially uncharged. Which one of the following expressions describes the current I(t) (in mA) for t > 0 ?
Consider the configuration shown in the figure which is a portion of a larger electrical network For R = 1 and currents , , , which one of the following is TRUE ?
For maximum power transfer between two cascaded sections of an electrical network, the relationship between the output impedance of the first section to the input impedance of the second section is
In the figure shown, the ideal switch has been open for a long time. If it is closed at t = 0, then the magnitude of the current (in mA) through the 4 k resistance at t = is _____.
For the Y network shown in the figure, the value of (in ) in the equivalent -network is____.
For the two-port network shown in the figure, the impedance (Z) matrix (in ) is
The circuit shown in the figure represents a
A series RC circuit is connected to a DC voltage source at time t = 0. The relation between the source voltage , the resistance R, the capacitance C, and the current is given below : Which one of the
Consider the building block called 'Network N ' shown in the figure. Let C = 100 F and R = 10 k . Two such blocks are connected in cascade as shown in the figure. The transfer function of the cascaded
In the circuit shown in the figure, the value of (in volts) for is____.
The steady state output of the circuit shown in the figure is given by . If the amplitude = 0.25, then the frequency is
For an all-pass system , where , for all . If Re , Im , then b equals
A system is described by the following differential equation, where u(t) is the input to the system and y(t) is the output of the system. when y(0) = 1 and u(t) is a unit step function, y(t) is
The N -point DFT X of a sequence x[n], is given by, , Denote this relation as . For N=4, which one of the following sequences satisfies ?
Let x[n] = x[-n]. Let X(z) be the z -transform of x[n]. If 0.5+j0.25 is a zero of X(z), which one of the following must also be a zero of X(z).
A causal LTI system has zero initial conditions and impulse response . Its input and output are related through the linear constant-coefficient differential equation Let another signal be defined as I
The unilateral Laplace transform of is . Which one of the following is the unilateral Laplace transform of ?
Let h(t) denote the impulse response of a causal system with transfer function . Consider the following three statements. S1 : The system is stable S2: is independent of S3 : A non-causal system with
The value of the integral is ____.
The z-transform of the sequence x[n] is given by , with the region of convergence |z| > 2. Then, x[2] is ____.
Consider a discrete time periodic signal . Let be the complex Fourier series coefficients of x[n]. The coefficients are non-zero when k = Bm 1, where m is any integer. The value of B is ____.
A continuous, linear time-invariant filter has an impulse response h(t) described by When a constant input of values 5 is applied to this filter, the steady state output is_____.
Let . The Region of Convergence (ROC) of the z -transform of x[n].
A real-valued signal x(t) limited to the frequency band is passed through a linear time invariant system whose frequency response is The output of the system is
For a function g(t), it is given that for any real value . If , then is
The input-output relationship of a causal stable LTI system is given as y[n -1]+ If the impulse response h[n] of this system satisfies the condition , the relationship between and is
For a given sample-and-hold circuit, if the value of the hold capacitor is increased, then
Let , , . The quantities are real numbers. Consider . If the zero of lies on the unit circle, then = ____.
A discrete time signal , being an integer, is
Consider the periodic square wave in the figure shown. The ratio of the power in the harmonic to the power in the harmonic for this waveform is closest in value to ______.
The phase response of a passband waveform at the receiver is given by where is the centre frequency, and and are positive constants. The actual signal propagation delay from the transmitter to receive
Consider two real valued signals, x(t) band-limited to [-500 Hz, 500 Hz] and y(t) band-limited to [-1 kHz, 1 kHz]. For , the Nyquist sampling frequency (in kHz) is ____.
The input , where u(t) is the unit step function, is applied to a system with transfer function . If the initial value of the output is -2, then the value of the output at steady state is _____.
An FIR system is described by the system function The system is
The sequence , where u[n] is the unit step sequence, is convolved with itself to obtain y[n]. Then is _____.
Consider a discrete-time signal If y[n] is the convolution of x[n] with itself, the value of y[4] is _____.
Let be sampled at 20 Hz and reconstructed using an ideal low-pass filter with cut-off frequency of 20 Hz. The frequency/ frequencies present in the reconstructed signal is/are
A stable linear time invariant (LTI) system has a transfer function . To make this system causal it needs to be cascaded with another LTI system having a transfer function . A correct choice for among
A Fourier transform pair is given by where u [n] denotes the unit step sequence. The values of A is _____.