ECIL Placement Paper

Company: Electronics Corporation of India Limited

31.A negative feedback is applied to an amplifier with the feedback voltage proportional to the output current. This feedback increases the
a) input impedance of the amplifier
b) output impedance of the amplifier
c) distortion in the amplifier
d) gain of the amplifier

32.The early effect in a BJT is modeled by the small signal parameter
a) r0
b) r∏
c) gm
d) β

33.For a given filter order, which one of the following type of filters has the least amount of ripple both in pass‐band and stop‐band?
a) Chebyshev type I
b) Bessel
c) Chebyshev type II
d) Elliptic

34.For a practical feedback circuit to have sustained oscillation, the most appropriate value of the loop gain T is
a) 1
b) ‐1
c) ‐1.02
d) 1.02

35.Assume the op‐amps in given figure to be ideal. If the input signal vi is a sinusoid of 2V peak‐to‐peak and with zero DC component, the output signal vo is a
a) sine wave
b) square wave
c) pulse train
d) triangular wave

36.In a common source amplifier, the mid‐band voltage gain is 40 dB and the upper cutoff frequency is 150kHz. Assuming single pole approximation for the amplifier the unity gain frequency fT is
a) 6 MHz
b) 15 MHz
c) 150 MHz
d) 1.5 GHz

37.An op‐amp is ideal except for finite gain and CMRR. Given the open loop differential gain Ad=2000,CMRR = 1000, the input to the noninverting terminal is 5.002 V and the input to the inverting terminal is 4.999 V, the output voltage of the op‐amp is
a) 14 V
b) 24 V
c) ‐6 V
d) ‐8 V

38.The op‐amp in the circuit in given figure has a non‐zero DC offset. The steady state value of the output voltage Vo is
a) –RC dvs(t)/ dt
b) – (1/RC)|vs(t)dt
c) –V
d) +V

39.For the circuit in given figure, if the value of the capacitor C is doubled, the duty‐cycle of the output waveform Vo
a) increases by a factor of 2
b) increases by a factor of 1.44
c) remains constant
d) decreases by a factor of 1.44

40.Assume the op‐amp in the given circuit to be ideal. The value of the output voltage Vo is
a) 3.2 Vi
b) 4 Vi
c) 9 Vi
d) 10 Vi

41.The complement of the Boolean expression F = (X + Yˉ + Z)(Xˉ + Zˉ)(X + Y) is
a) XYZ+XZˉ+YˉZ
b) XˉYZˉ+XZ+XˉYˉ
c) XˉYZˉ+XZ+YZ
d) XYZ+XˉYˉ

42.The Boolean function F(A,B,C,D) = ∑(0,6,8,13,14) with don’t care conditions d(A,B,C,D) = ∑(2,4,10) can be simplified to
a) F = BˉDˉ+CDˉ+ABCˉ
b) F = BˉDˉ+CDˉ+ABCˉD
c) F = ABˉDˉ+CDˉ+ABCˉ
d) F = BˉDˉ+CDˉ+ABCD

43.The Boolean function F = AˉDˉ+BˉD can be realized by one of the following figures

44. For the multiplexer in given figure, the Boolean expression for the output Y is
a) AˉBˉ+BˉCˉ+AC
b) ABˉ+BˉCˉ+ACˉ
c) ABˉ+BˉC+AC
d) AˉBˉ+BˉC+AˉC

45. Which one of the following is TRUE?
a) Both latch and flip‐flop are edge triggered.
b) A latch is level triggered and a flip‐flop is edge triggered.
c) A latch is edge triggered and a flip‐flop is level triggered.
d) Both latch and flip‐flop are level triggered.

46. In a schottky TTL gate, the Schottky diode
a) increases the propagation delay
b) increases the power consumption
c) prevents saturation of the output transistor
d) keeps the transistor in cutoff region

47. For which one of the following ultraviolet light is used to erase the stored contents
a) PROM
b) EPROM
c) EEPROM
d) PLA

48. Which one of the following is NOT a synchronous counter
a) Johnson counter
b) Ring counter
c) Ripple counter
d) Up‐down counter

49. In 8085 microprocessor, the accumulator is a
a) 4 bit register
b) 8 bit register
c) 16 bit register
d) 32 bit register

50. In the register indirect addressing mode of 8085 microprocessor, data is stored
a) at the address contained in the register pair
b) in the register pair
c) in the accumulator
d) in a fixed location of the memory

51. The output w[n] of the system shown in given figure is
a) x[n]
b) x[n‐1]
c) x[n] – x[n‐1]
d) 0.5(x[n‐1] + x[n])

52. Which one of the following is a periodic signal
a) x(t) = 2 e^j(t+(π/4))
b) x[n] = u[n] + u[‐n]
c) x[n] = ∑{∂[n‐4k]‐∂[n‐1‐4k]} where k = ‐∞to ∞
d) x(t) = e^ (‐1+j)t

53. If the input‐output relation of a system is y(t) = ∫x(t) dt where t = ‐∞ to 2t
a) linear, time‐invariant and unstable
b) linear, non‐causal and unstable
c) linear, causal and time invariant
d) non‐causal, time invariant and unstable

54. Which one of the can be the magnitude of the transfer function | H(jw) | of a causal system

55. Consider the function H(jw) = H1(w) + jH2(w), where H1(w) is an odd function and H2(w) is an even function. The inverse Fourier transform of H(jw) is
a) a real and odd function b) a complex function
c) a purely imaginary function
d) a purely imaginary and odd function

56. The laplace transform of given signal is
a) –A((1‐e^cs)/s)
b) A((1‐e^cs)/s)
c) A((1‐e^‐cs)/s)
d) –A((1‐e^‐cs)/s)

57. If X(z) is the z‐transform of x[n] = (1/2)^ |n|, the ROC of X(z) is
a) |z| >
b) |z| < 2
c) 0.5<|z|<2
d) the entire z‐plane

58. In a linear phase system, τg the group delay and τp the phase delay are
a) constant and equal to each other
b) τg is a constant and τp is proportional to w
c) a constant and τg is proportional to w
d) τg is proportional to w and τp is proportional to w

59. A signal m(t), band‐limited to a maximum frequency of 20 kHz is sampled at a frequency fs kHz to generate s(t). An ideal low pass filter having cut‐off frequency 37 kHz is used to reconstruct m(t) from s(t). The maximum value of fs required to reconstruct m(t) without distortion is
a) 20 kHz
b) 40kHz
c) 57 kHz

60. If the signal x(t) shown in given figure is fed to an LTI system having impulse response h(t) as shown in given figure, the value of the DC component present in the output y(t) is
a) 1
b) 2
c) 3
d) 4

ECIL Placement Paper