Model Questions on Diploma Electronics Engineering

1. The maximum theoretical efficiency for class A amplifier is
(a) 12.5%
(b) 25 %
(c) 50%
(d) 75%

2. If it is desired to have low output impedance in an amplifier circuit then we should use
(a) common collector circuit
(b) common base circuit
(c) common emitter circuit
(d) either (b) or (c)

3. Which amplifier has the highest power gain?
(a) common collector
(b) common base
(c) common emitter
(d) both CC and CE

4. Which amplifier has a voltage again of less than unity?
(a) common base
(b) common collector
(c) common emitter
(d) both CB and CC

5. For class B operation the theoretical maximum efficiency is
(a) 100%
(b) 78.5%
(c) 50%
(d) 27.5%

6. A push pull amplifier is a
(a) power amplifier
(b) voltage amplifier
(c) current amplifier
(d) both (a) and (c)

7. If the mid band gain of an amplifier is 40dB, the gain at half power frequency is
(a) 37dB
(b) 30dB
(c) 20dB
(d) 13dB

8. The purpose of impedance matching in an amplifier circuit is to achieve
(a) high frequency
(b) reduced distortion
(c) maximum power transfer
(d) none of these

9. A transistor amplifier is operating in class A mode. If a transformer is connected for impedance matching, the efficiency will
(a) increase
(b) decrease
(c) not affected
(d) may increase or decrease

10. At mid band frequencies the coupling capacitor of an RC coupled CE amplifier may be considered as
(a) open circuit
(b) short circuit
(c) an inductance
(d) none of these

11. Which of the following amplifier circuits have highest input impedance?
(a) circuit using BJT
(b) circuit using JFET
(c) circuit using MOSFET
(d) either (a) or (b)

12. The open loop gain of an amplifier is 200. If negative feedback with β=0.2 is used, the closed loop gain will be
(a) 200
(b) 40.12
(c) 4.878
(d) 2.2

13. The open loop gain of an amplifier is 50 but is likely to decrease by 20% due to various factors. If negative feedback with β=0.1 is used the change in gain will be about
(a) 20%
(b) 10%
(c) 3.33%
(d) 0.5%

14. The input to an Op-Amp integrating amplifier is constant voltage. The output will be a
(a) constant voltage
(b) saw tooth wave
(c) ramp voltage
(d) any ac wave

15. The element in the feedback circuit of a logarithmic amplifier using Op-Amp is a
(a) Resistor
(b) Capacitor
(c) Inductor
(d) diode

16. As compared to full wave rectifier, a half wave rectifier has
(a) higher ripple factor
(b) lower ripple factor
(c) same ripple factor
(d) none of these

17. A rectifier circuit has load resistance R and uses a capacitor filter having capacitance C. For low ripple in the output, the value of RC should be
(a) One
(b) Low
(c) high
(d) neither low nor high

18. A Hartley oscillator uses
(a) tapped inductor
(b) tapped capacitor
(c) both (a) and (b)
(d) neither (a) nor (b)

19. A potential of 7V is applied to a silicon diode in series with a 1KΩ load resistor. If the diode is forward biased, then the current in the circuit is
(a) 7mA
(b) 6.3mA
(c) 0.7mA
(d) zero

20. If input frequency is 50Hz, the frequency of output wave in a full wave diode rectifier circuit is
(a) 25Hz
(b) 50Hz
(c) 100Hz
(d) 200Hz

21. The dc load current in a bridge rectifier circuit is 10mA. The dc load current through each diode is
(a) 40mA
(b) 20mA
(c) 10mA
(d) 5mA

22. In a bridge rectifier circuit the r.m.s. value of input ac voltage is 10V. The PIV across each diode is
(a) 7.07V
(b) 10V
(c) 14.14V
(d) 28.28V

23. In a self bias circuit for CE amplifier, the base voltage is
(a) equal to supply voltage
(b) more than supply voltage
(c) less than supply voltage
(d) none of these

24. The self bias provides
(a) stable Q point
(b) large voltage gain
(c) high input impedance
(d) high base current

25. For dc the current through coupling capacitor in CE amplifier circuit is
(a) very high
(b) high
(c) low
(d) zero

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26. A bypass capacitor produces
(a) dc ground
(b) ac ground
(c) both (a) & (b)
(d) none of these

27. In deriving ac equivalent circuit for an amplifier circuit we short circuit all
(a) Resistors
(b) Inductors
(c) Transistors
(d) capacitors

28. When the ac base voltage in a CE amplifier circuit is too high, the ac emitter current is
(a) Zero
(b) Constant
(c) Alternating
(d) distorted

29. In a CE amplifier circuit, the output voltage
(a) is very small
(b) depends on β
(c) is always constant
(d) none of these

30. In a two stage CE amplifier circuit, the collector resistance of the first stage depends on
(a) load resistance
(b) input impedance of first stage
(c) input impedance of 2nd stage
(d) all of the above

31. In a CE amplifier circuit the emitter by pass capacitor is removed. The ac output voltage
(a) increase
(b) remains same
(c) decreases
(d) increase or decreases

32. The purpose of connecting a coupling capacitor in the output circuit of an amplifier is
(a) to increase voltage gain
(b) to increase collector current
(c) to block dc collector voltage
(d) all of these

33. A class A transformer coupled power amplifier is to deliver 10W output. The power rating of transistor should not be less than
(a) 5W
(b) 10W
(c) 20W
(d) 40W

34. In a differential amplifier, CMRR can be improved by using an increased
(a) emitter resistance
(b) collector resistance
(c) power supply voltage
(d) source resistance

35. Crossover distortion behaviour is a characteristic of
(a) Class A
(b) Class B
(c) Class AB
(d) Class C

36. Negative feedback in amplifier
(a) reduces gain
(b) increases frequency and phase distortion
(c) reduces bandwidth
(d) increases noise

37. The early effect in BJT is caused by
(a) fast turn on
(b) fast turn off
(c) large collector base reverse bias
(d) large emitter base forward bias

38. If the Q of a single stage, single tuned amplifier is doubled, the bandwidth will be
(a) Same
(b) Halved
(c) doubled
(d) quadrupled

39. In every practical oscillator the loop gain is slightly more than unity and amplitude of oscillations is limited by
(a) magnitude of loop gain
(b) onset of non linearity
(c) magnitude of gain
(d) feedback factor

40. In an Op-Amp comparator, the positive or negative output is
(a) Saturated
(b) Amplified
(c) un-saturated
(d) any of the above

41. In an RC phase shift oscillator, the total phase shift of the three RC lead network is
(a) 360º
(b) 180º
(c) 90º
(d) 0º

42. An OP-Amp uses
(a) RC coupling
(b) direct coupling
(c) transformer coupling
(d) either (b) or (c)

43. Which of the following is difficult to be fabricated in a monolithic IC?
(a) inductors
(b) large capacitors
(c) small capacitors
(d) both (a) and (b)

44. FET can be used in
(a) buffer amplifier circuits
(b) cascade amplifier circuits
(c) digital circuits
(d) all of the above circuits

45. In a class C power amplifier the input frequency of ac signal is 1MHz. If tank circuit has C=1000pF, the value of L is
(a) 25μH
(b) 50μH
(c) 100μH
(d) 200μH

46. If the output current wave shape of class C circuit has a period 1μsec and pulse width of 0.006μsec, the duty cycle is
(a) 6%
(b) 0.6%
(c) 0.06%
(d) 0.006%

47. Transformer coupling is mostly used in
(a) RF amplifier
(b) audio amplifier
(c) both (a) and (b)
(d) None of these

48. In a CE amplifier the ac cut-off voltage is 9V and slope of ac load line is –0.5mA/V, the ac saturation current is
(a) 18mA
(b) 9mA
(c) 4.5mA
(d) 3mA

49. A CB amplifier has re=6Ω, RL=600Ω and ά =0.98. The voltage gain is
(a) 88
(b) 100
(c) 98
(d) 6

50. The disadvantage of direct coupled amplifier is
(a) Drift
(b) large size of BJT
(c) low voltage gain
(d) both (b) and (c)