Design of Electronic Devices & Circuits - MCQ from AMIE exams (Summer 2021)

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Multiple Choice Questions: (10 x 2)

1. Assume the OP-Amp to be ideal, the voltage gain of the amplifier as shown is:
(a) -R2/R1
(b) -R3/R1
(c) -R2∥R3/R1
(d) -(R2+R3)/R1

2. In the rectifier signal level diode 1N4007 can be connected with
(a) With the 220 V AC power supply
(b) With the 220 V DC power supply
(c) With the 12 V AC power supply
(d) With the 12 V DC power supply

3. Suppose that the modulating signal is m(t)=2cos(2πfmt) and the carrier signal is xc(t) = Accos(2πfct), which one of the following is a conventional AM signal without over-modulation?
(a) x(t) = {A_c}.m(t).\cos (2\pi {f_c}t)
(b) x(t) = {A_c}.[1 + m(t)].\cos (2\pi {f_c}t)
(c) x(t) = {A_c}.\cos (2\pi {f_c}t) + {A_c}/4m(t).\cos (2\pi {f_c}t)
(d) x(t) = {A_c}.\cos (2\pi {f_m}t).\cos (2\pi {f_c}t) + {A_c}\sin (2\pi {f_m}t)\sin (2\pi {f_c}t)

4. The ideal Op Amp has the following characteristics
(a) Ri = ∞; Av = ∞; R0 = 0
(b) Ri = 0; Av = ∞; R0 = 0
(c) Ri = 0; Av = 0; R0 = 0
(d) Ri = ∞; Av = ∞; R0 = ∞

5. In quartz watches which oscillator is preferred
(a) RC phase shift oscillator
(b) Quartz crystal oscillator
(c) Wein Bridge oscillator
(d) None of these

6. Which type of Analog to Digital Converter is the fastest
(a) Successive approximation register
(b) Dual slope ADC
(c) Flash ADC
(d) Pipelined ADC

7. Assume that the op-amp of Fig. is ideal. If Vi is a triangular wave, then the output waveform will be
(a) Square wave
(b) Triangular wave
(c) Parabolic wave
(d) Sine wave

8. An ideal Op-Amp is a
(a) Voltage-controlled current source 
(b) Voltage-controlled voltage source 
(c) Current controlled current source 
(d) Current-controlled voltage source

9. From the power saving option which modulation technique is preferred
(a) AM
(b) DSBSC
(c) VSB
(d) FM

10. The phenomenon of overlapping of adjacent bits due to pulse spreading is
(a) Scattering
(b) Dispersion
(c) Attenuation
(d) Intersymbol Interference

Answers

1. (a)

3. (c) 

4. (a) The ideal op-amp has the following characteristics:
  • Input impedance (Differential or Common-mode) Rin = Infinity
  • Output impedance (open loop) R0= 0
  • Gain A = Infinity
  • Infinite Bandwidth
  • Common-mode voltage gain = 0
  • Vout = 0 when both inputs are at the same voltage, i.e. (zero "offset voltage")
5. (b) Quartz is used in watches as it acts as a piezoelectric oscillator.

6. (c) The fastest type of Analog to Digital converter is the Flash type/Parallel comparator type.

7. (a)

8. (b) Vout = A x Vin

9. (b) DSB -SC is a form of Amplitude modulation where only the sidebands are transmitted and the carrier is suppressed. The advantage is 66% power saving compared to conventional AM. 

10. (d) Inter-symbol Interference: This is the effect of dispersion on optical fibre. Intersymbol interference occurs when the pulse spreading caused by dispersion causes the output pulses of a system to overlap.
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