About Transistors

A transistor is a semiconductor device used to amplify or switch electronic signals and electrical power.

The transistor is one of the most important inventions of the 20th century and it is still used in many electronic devices today. The transistor was invented in 1947 by John Bardeen, Walter Brattain, and William Shockley at Bell Laboratories. The transistor was a big improvement over the vacuum tube because it was smaller, more reliable, and cheaper to produce. The transistor revolutionized the electronics industry and paved the way for the development of the integrated circuit (IC).Today, some transistors are packaged individually, but many more are found embedded in integrated circuits.

Following are some of the multiple choice questions on the Transistors with answers that will help the students in developing their knowledge.

Transistors MCQ

1. IC = [a / (1 - a )] IB + ___________

  • ICEO
  • ICBO
  • IC
  • (1 - a ) IB

2. An ideal value of stability factor is ___________

  • 100
  • 200
  • More than 200
  • 1

3. In a transistor amplifier circuit VCE = VCB + ___________

  • VBE
  • 2 VBE
  • 5 VBE
  • None of the above

4. A transistor is connected in CB mode. If it is not connected in CE mode with same bias voltages, the values of IE, IB and IC will ___________

  • remain the same
  • increase
  • decrease
  • none of the above

5. The leakage current in CE arrangement is ___________ that in CB arrangement

  • more than
  • less than
  • the same as
  • none of the above

6. If the value of collector current IC increases, then the value of VCE ___________

  • Remains the same
  • Decreases
  • Increases
  • None of the above

7. Most of the majority carriers from the emitter ___________

  • recombine in the base
  • recombine in the emitter
  • pass through the base region to the collector
  • none of the above

8. In a tansistor, IC = 100 mA and IE = 100.2 mA. The value of ß is ___________

  • 100
  • 50
  • about 1
  • 200

9. A tuned amplifier is used in ___________ applications

  • Radio frequency
  • Low frequency
  • Audio frequency
  • None of the above

10. If Q of an LC circuit increases, then bandwidth ___________

  • Increases
  • Decreases
  • Remains the same
  • Insufficient data

11. The power gain in a transistor connected in ___________ arrangement is the highest

  • common emitter
  • common base
  • common collector
  • none of the above

12. At series or parallel resonance, the circuit power factor is ___________

  • 0%
  • 5%
  • 10%
  • 8%

13. A silicon transistor is biased with base resistor method. If ß=100, VBE =0.7 V, zero signal collector current IC = 1 mA and VCC = 6V , what is the value of the base resistor RB?

  • 105 kΩ
  • 530 kΩ
  • 315 kΩ
  • None of the above

14. The base of a transistor is ___________ doped

  • heavily
  • moderately
  • lightly
  • none of the above

15. In a npn transistor, ___________ are the minority carriers

  • free electrons
  • holes
  • donor ions
  • acceptor ions

16. ICEO = () ICBO

  • ß
  • 1 + a
  • 1 + ß
  • none of the above

17. In a pnp transistor, the current carriers are ___________

  • acceptor ions
  • donor ions
  • free electrons
  • holes

18. The biasing circuit has a stability factor of 50. If due to temperature change, ICBO changes by 1 µA, then IC will change by ___________

  • 100 µA
  • 25 µA
  • 20 µA
  • 50 µA

19. Tuned class C amplifiers are used for RF signals of ___________

  • Low power
  • High power
  • Very high power
  • None of the above

20. The Q of an LC circuit is given by ___________

  • 2pfr x R
  • R / 2pfrL
  • 2pfrL / R
  • R2/2pfrL

21. For proper amplification by a transistor circuit, the operating point should be located at the ___________ of the d.c. load line

  • The end point
  • Middle
  • The maximum current point
  • None of the above

22. The leakage current in a silicon transistor is about ___________ the leakage current in a germanium transistor

  • One hundredth
  • One tenth
  • One thousandth
  • One millionth

23. In a transistor if ß = 100 and collector current is 10 mA, then IE is ___________

  • 100 mA
  • 10.1 mA
  • 110 mA
  • none of the above

24. The Q of a tuned amplifier is generally ___________

  • Less than 5
  • Less than 10
  • More than 10
  • None of the above

25. The value of ß for a transistor is generally ___________

  • 1
  • less than 1
  • between 20 and 500
  • above 500

26. If the maximum collector current due to signal alone is 3 mA, then zero signal collector current should be at least equal to ___________

  • 6 mA
  • 3 mA
  • 2 mA
  • 1 mA

27. The purpose of resistance in the emitter circuit of a transistor amplifier is to ___________

  • Limit the change in emitter current
  • Provide base-emitter bias
  • Limit the maximum emitter current
  • None of the above

28. The voltage gain in a transistor connected in ___________ arrangement is the highest

  • common base
  • common collector
  • common emitter
  • none of the above

29. The output impedance of a transistor connected in ___________ arrangement is the highest

  • common emitter
  • common collector
  • common base
  • none of the above

30. The input impedance of a transistor connected in ___________ arrangement is the highest

  • common emitter
  • common collector
  • common base
  • none of the above

31. The phase difference between the input and output voltages of a transistor connected in common collector arrangement is ___________

  • 90°
  • 180°
  • 270°

32. The voltage gain of a transistor connected in common collector arrangement is ___________

  • equal to 1
  • more than 10
  • more than 100
  • less than 1

33. If the temperature increases, the value of VCE ___________

  • Remains the same
  • Is increased
  • Is decreased
  • None of the above

34. Frequencies above ___________ kHz are called radio frequencies

  • 2
  • 10
  • 50
  • 200

35. The phase difference between the input and output voltages in a common base arrangement is ___________

  • 90°
  • 270°
  • 180°

36. In the above question, what are the values of cut-off frequencies?

  • 140 kHz , 60 kHz
  • 1020 kHz , 980 kHz
  • 1030 kHz , 970 kHz
  • None of the above

37. In a parallel LC circuit, if the signal frequency is decreased below the resonant frequency, then ___________

  • XL decreases and XC increases
  • XL increases and XC decreases
  • Line current becomes minimum
  • None of the above

38. In parallel resonance, the circuit impedance is ___________

  • C/LR
  • R/LC
  • CR/L
  • L/CR

39. Transistor biasing is generally provided by a ___________

  • Biasing circuit
  • Bias battery
  • Diode
  • None of the above

40. The value of VBE ___________

  • Depends upon IC to moderate extent
  • Is almost independent of IC
  • Is strongly dependant on IC
  • None of the above

41. In a transistor ___________

  • IC = IE + IB
  • IB = IC + IE
  • IE = IC - IB
  • IE = IC + IB

42. In the double tuned circuit, if the mutual inductance between the two tuned circuits is decreased, the level of resonance curve ___________

  • Remains the same
  • Is lowered
  • Is raised
  • None of the above

43. The arrow in the symbol of a transistor indicates the direction of ___________

  • electron current in the emitter
  • electron current in the collector
  • hole current in the emitter
  • donor ion current

44. The relation between ß and a is ___________

  • ß = a / (1 – a )
  • ß = (1 – a ) / a
  • ß = 1 / (1 – a )
  • ß = a / (1 + a )

45. For faithful amplification by a transistor circuit, the value of VBE should ___________ for a silicon transistor

  • Be zero
  • Be 0.01 V
  • Not fall below 0.7 V
  • Be between 0 V and 0.1 V

46. IC = ß IB + ___________

  • ICBO
  • IC
  • aIE
  • ICEO

47. If a high degree of selectivity is desired, then double-tuned circuit should have ___________ coupling

  • Loose
  • Tight
  • Critical
  • None of the above

48. A resonant circuit contains ___________ elements

  • R and L only
  • R and C only
  • Only R
  • L and C

49. Transistor biasing represents ___________ conditions

  • a.c.
  • d.c.
  • both a.c. and d.c.
  • none of the above

50. At series resonance, the circuit offers ___________ impedance

  • Zero
  • Maximum
  • Minimum
  • None of the above

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