Question Bank

Unit-1

1. For which type of material, the number of free elec

electron
tron concentration is equal to the number of donor
atoms?
a) P type semiconductor
b) Metal
c) N-type semiconductor
d) Insulator
e) None of the above

2. In diffusion, the
he particles flow from a region of _______ concentration to region of
___________concentration
a) High, low
b) Low , high
c) High , medium
d) Low, medium
e) None of the above

3. If the positive terminal of the battery is connected

connecte to the anode of the diode, then it is known as
a) Forward biased
b) Reverse biased
c) Equilibrium
d) No Bias
e) None of the above

4. During reverse bias, a small current develops known as a

a) Forward current
b) Passive current
c) Reverse saturation current
d) Active current
e) None of the above

5. Which of the factors change the diode current?

a) Temperature
b) External voltage applied to the diode
c) Boltzmann‘s constant
d) Resistance
e) None of the above

6. The voltage
ge equivalent of temperature (VT) in diode current equation is equal to
a) T/1000 volts
b) T/300 volts
c) T/1600 volts
d) T/11600 volts
 e) None of the above

7. .The
The cut off voltage for diode of silicon semiconduc
semiconductor
tor and germanium semiconductor is ____ volts.
a) 0.5 and 0.1
b) 0.7 and 0.3
c) 1 and 0.5
d) 0.5 and 1
e) None of the above
8. For an ideal diode which of the following is true?
a) It allows the passage of current in the forward bia
biass with zero potential drop across the diode
b) It does not allow the flow of current in reverse bias
bi
c) It works as open circuit in reverse bias
d) It works as short circuit in reverse bias
e) None of the above

9. for the given circuit find the output waveform

a) b)

c) d)

e) None of the above

10. The diode in a half wave rectifier

fier has a forward resistance RF. The voltage is Vmsinωt and the load
resistance is RL. The DC current is given by
a) Vm/√2RL
b) Vm/(RF+RL)π
c) 2Vm/√π
d) Vm/RL
e) None of the above

11. Efficiency of a half wave rectifier is

a) 50%
b) 60%
c) 40.6%
d) 46%
 e) None of the above

12. If peak voltage for a half wave rectifier circuit iis 5V and diode cut in voltage is 0.7, then peak
inverse voltage on diode will be?
a) 5V
b) 4.9V
c) 4.3V
d) 6.7V
e) None of the above

13. Ripple factor of a half wave rectifier is

a) 1.414
b) 1.21
c) 1.4
d) 0.48
e) None of the above

14. A full wave rectifier uses load resistor of 1500Ω.

1500 Assume the diodes have Rf=10Ω,
=10 Rr=∞. The
voltage applied to diode is 30V with a frequency of 50Hz. Calculate the AC power input.
a) 368.98mW
b) 275.2mW
c) 0.298 W
d) 298.01mW
e) None of the above
15. Efficiency of a centre tapped full wave rectifier is
i _________
a) 50%
b) 46%
c) 70%
d) 81.2%
e) None of the above
16. DC average current of a full wave rectifier is equal to
a) 2Im
b) 2Im/π
c) Im/2
d) 0.636 Im
e) None of the above *(where Im is the maximum peak current of input)

17. Ripple factor of full wave rectifier

tifier is?
a) 1.414
b) 1.212
c) 0.482
d) 1.321
e) None of the above
18. A diode for which you can change the reverse bias, and thus vary the capacitance is called a
a) Varactor diode
b) tunnel diode
c) zener diode
d) photo diode
 e) None of the above

19. What is the current through

hrough the diode?

a) 1 mA
b) 0.975 mA
c) 0.942 mA
d) 0.0 mA
e) None of the above

20. What is the current through the zener diode?

a) 0 mA
b) 7 mA
c) 8.3 mA
d) 13 mA
e) None of the above

21. With a 12 V supply, a silicon diode, and a 370-ohm

370 resistor in series, what voltage will be dropped
across the diode?
a) 0.3 V
b) 0.7 V
c) 0.9 V
d) 1.4 V
e) None of the above
22. Determine ID.

a) 0 mA
b) 1.893 mA
c) 2.036 mA
d) 2.143 mA
e) None of the above

23. What describes the circuit?

a) Full-wave rectifier
b) Half-wave rectifier
c) Clipper
d) Clamper
e) None of the above

24. With this Zener diode in its "on state," what is th

the level of IZ for the maximum load resistance?

a) 0 mA
b) Undefined
c) Equal to IRL
d) IZM
e) None of the above
26. LEDs are made out of
a) silicon
b) Germanium
c) Gallium Arsenide.
d) Gallium phosphide
e) None of the above

termine the peak for both half cycles of the output waveform.
27. Determine

a) 16 V, –4 V
b) 16 V, 4 V
c) –16 V, 4 V
d) –16 V, –4 V
e) None of the above
28. Determine V2.

a) 3.201 V
b) 0 V
c) 4.3 V
d) 1.371 V
e) None of the above

29. which of the following atoms may be use

used as P-type majority
a) Arsenic
b) Boron
c) Phosphorous
d) Aluminum
e) None of the above
30. Avalanche breakdown in a semiconductor diode occurs if
a) Forward Current Exceeds A Certain Value
b) Reverse Bias Exceeds A Certain Value
c) Forward Bias Exceeds A Certain Value
V
d) Potential Barrier Reduced To Zero
e) None Of These

UNIT II

31. When transistors are used in digital circuits they usually operate in the:
a) Active region
b) Breakdown region
c) Saturation and cutoff region
d) Linear region
e) All of the above

32. In a BJT
a) The base region is sandwiched between emitter and ccollector
b) The collector is sandwiched between base and emitte
emitter
c) The emitter region is sandwiched between base and collector
c
d) The emitter region is sandwich
sandwiched between n and p regions
e) None of the above

33. If the current gain is 200 and the collector current

curren is 100 mA,, Then the base current is:
a) 2 mA
b) 2 A
c) 20 mA
d) 0.5 mA
e) None of the above

34. The base regionn of an npn transistor is thin and

a) Heavily doped
b) Lightly doped
c) Metallic
d) Doped by penta-valent
valent material
e) All of the above

35. Inn a common base BJT connection IC = 0.96 mA and IB = 0.05 mA. α is equal to
a) 9.5
b) 0.95
c) 95
d) 0.095
e) None of the above
36. In a transistor circuit IE = 5mA, IC = 4.95 mA, β is
a) 100
b) 90
c) 99
d) 60
e) None of the above

37. Inn a BJT circuit, a PNP transistor is replaced by NP

NPNN transistor to analyse the new circuit
a) All calculations done earlier have to be separated
b)) Replace all calculated voltages by reverse values
c)) Replace all calculated currents by reverse val
values
d) No modification required
e) None of the above

38. In common base connection, the emitter current is 1 mA. If the emitter side is open, the collector
current is 60 µA. The total collector current for α = 0.93 is :
a) 9.9 mA
b) 10 mA
c) 100 mA
d) 0.99 mA
e) None of the above

39. Which of the following junction

ion under reverse bias causes a small collector
ollector current with emitter
terminal open:
a) Collector junction
b) Base junction
c) Emitter junction
d) Transistor
e) All of the above

40. The emitter current IE in a transistor is 4 mA. If the leakage current ICBO is 6 µA and α is 0.98, the
collector current has the value :
a) 3.0 mA
b) 2.0 mA
c) 3.926 A
d) 3.926 mA
e) None of the above

41. An emitter in a BJT is doped much more heavily than the base as it

a)) Increases the emitter efficiency

b) Decreases base current
c) Has no effect
d) All of the above
e) None of the above
42. In cut off region operation of a transistor
a) Both junctions are forward biased
b)) Both junctions are reverse biased
c)) Emitter junction is forward biased while collecto
collector junction is reverse biased
d)) Emitter junction is reverse biased while collecto
collector junction is forward biased
e) All of the above

43. In a transistor β may be expressed in terms of α as

a)

b)

c)

d)
e) None of the above

44. An increase in the magnitude of the applied reverse bias voltage at collector junction results in
a) Increase in depletion region w
width
b) Increase in IE and IC
c) Increase in IB
d) All of the above
e) None of the above

45. Consider the following statements S1 and S2

S1: the β of a bipolar transistor reduces if the base width is increased
S2: the β of a bipolar transistor increases if tthe
he doping concentration in the base is increased
Which one of the following is correct?
a) S1 is false and S2 is true
b) Both S1 and S2 are true
c) Both S1 and S2 are false
d) S2 is false and S1 is true
e) None of the above

46. An FET is essentially a

a) Current driven device
b) Voltage driven device
c) Power driven device
d) All of the above
e) None of the above

47. For N-channel JFET, IDSS = 20mA, VP = -8V. The drain current value at VGS = - 4V is:
a) 4mA
b) 0.5 mA
c) 50 mA
d) 5mA
 e) None of the above

48. For N-channel JFET, IDSS = 20mA, VP = -8V, and gm0 = 5000µs. The trans-conductance
conductance at VGS = -
4V is
a) 5000µS
b) 1000µS
c) 2500µS
d) 2000µS
e) None of the above

49. When a reverse bias is applied to the gate of JFET, the depletion region width
a) Is uniform in the channel
b)) Is wider near the source and tapers near the drain
drai
c)) Is wider near the drain and tapers near the source
sourc
d) Is nil
e) None of the above

50. The drain source voltage for VGS = 0, at which drain current becomes nearly constant,
constant is called:
a) Barrier voltage
b) Breakdown voltage
c) Pick-off voltage
d) Pinch-off voltage
e) None of the above

51. For an N-channel JFET IDSS = 8.7 mA, VP = - 3V and VGS = -1V. gm0 has the value:
a) 5.8mS
b) 3.8mS
c) 6.8mS
d) 4.8mS
e) None of the above

52. How is N - channel

hannel FET operated as an amplifier
a) With a forward bias gate source junction
b)) With a reverse bias gate source junction
c)) With an open gate source junction
d) All of the above
e) None of the above

53. Pinch-off voltage in a JFET is

a) The drain voltagee that gives zero drain current
b)) The gate source voltage that gives unity drain cu
current
c)) The gate to source voltage that gives zero drain current
d)) The drain voltage that gives infinite drain current
curre
e) None of the above
54. Input impedance of MOSFET is
a) Less than that of FET but more than BJT
b)) More than that of FET and BJT
c)) More than that of FET but less than BJT
d)) Less than that of FET and BJT
e) None of the above

55. Which of the following statements are not true in ccase of FET
a) It has high input impedance
b)) It is high gain device in comparison to BJT
c) It is bipolar device
d) It is voltage controlled device
e) It is simple to fabricate

56. FETs when compared to BJTs have

a) High input impedance
b)) Current flow due to majority carriers
c) Low input impedance
d)) Current flow due to minority carriers
e) None of the above

57. Which of the statements given are correct?

a) BJT is a current controlled device with high input impedance
b)) FET is a voltage controlled device with high input
inpu impedance
c)) BJT and FET can be used for amplification
d)) FET is a current controlled device with high input
inpu impedance
e) None of the above

58. A MOSFET can be used as

a) Carrier controlled capacitor
b) Voltage controlled capacitor
c) Current controlled inductor
d) Voltage controlled inductor
e) All of the above

59. The saturation current ID in FET equals

a) 1

b) 1
/
c) 1
d) 1
e) None of the above
60. The JFET can operate in
a) Depletion mode only
b) Enhancement mode only
c)) Either depletion or enhancement mode at a time
d)) Both depletion and enhancement mode simultaneously
simultaneousl
e) None of the above

UNIT-3

61. In the common mode of op-amp

a) both inputs are grounded
b) the outputs are connected together
c) an identical signal appears on both the inputs
d) the output signal is in-phase
phase with input
e) None of these
62. A voltage follower ……….
a) has a voltage gain of 1
b) is non-inverting
c) has feedback resistor
d) both a & b
e) None of these
63. A voltage summing amplifier has ________.
a) several inputs and several outputs
b) several inputs and one output
c) one input and several outputs
d) one input and one output
e) None of these
64. The Common-ModeMode Rejection Ratio (CMRR) is ……….
a) very high
b) very low
c) always unity
d) Unpredictable
e) None of these
65. What is the common-mode
mode rejection ratio with a differential gain of 50
50,000
,000 and a common-mode
common
gain of 2 ?
a) –87.9 dB
b) 25000
c) 87.9 dB
d) both b&c
e) None of these
66. The input resistance of an ideal op-amp
op is ……….
a) ∞
b) 0
c) 1 ohm
d) 500 ohm
e) None of these
67. Output of the following circuit:

Vi

a)
b)
c) 0
d) RC
e) None of these

68. The output resistance of an ideal op-amp

op is ……….
a) 0
b) ∞
c) 1000 ohm
d) 50 ohm
e) None of these

69. If ADM = 3500 and ACM = 0.35, the CMRR is ……….

a. 1225
b. 10,000
c. 80 dB
d. b and c both
e. None of these
70. The slew rate of an ideal op-amp
amp is ……….
a) 100 v/micro-sec
b) 0
c) ∞
d) 500 v/micro-sec
e) None of these
71. When the feedback is not applied to the Operational Amplifier, then it works as ________.
a) Open Loop Mode
b) Closed Loop Mode
c) Variable Loop Mode
d) Negative Loop Mode
e) None of these
72. The gain of an ideal op-amp
amp is ……….
a) 100 db
b) 0
c) ∞
d) 40 db
e) None of these
73. An Operational Amplifier consists of __________ inp
input terminals.

a) 1
b) 2
c) 3
d) 4
e) None of these
74. The output of inverting OPAMP is out of phase with respect to the input.
a) 90°
b) 180°
c) 0°
d) 360°
e) None of these
75. Operational Amplifier can be used as a
a) Comparator
b) Diode
c) Differentiator
d) a and c both
e) None of these
76. The use of negative feedback
a. reduces the voltage
ge gain of an Op
Op-amp
b. makes the Op-amp
amp oscillate
c. makes linear operation possible
d. Both a and c
e. None of these
77. What is the maximum number of inputs to a summing amplifier?
a
a) Ten inputs
b) Six inputs
c) There is no practical limit on the number of inputs
input
d) Twenty inputs
e) None of these
78.

Refer to above Figure . Assume R1 = R2 = R3 = R F = 10 KΩ . V1 = V2 = V3 = 2volt .The value of

is
a) -1 Volt
b) -2 Volt
c) -4 Volt
 d) -8 Volt
e) None of these
79. Calculate the overall voltage gain of the circuit iif R1 = 100 and Rf = 1 k .

a) – 1
b) -10
c) 11
d) 9
e) None of these
loop op
80. For the non-inverting closed-loop op-amp, calculate the input voltage if R1 = 100 , Rf = 1 k , and
Vout = 550 mV.
a) 0.05 V
b) –5 mV
c) 50 mV
d) a and c
e) None of these
81. An operational amplifier is a _____ gain and _____ bandwidth differential amplifier.
a) very low, narrow
b) low, wide
c) medium, narrow
d) very high, wide
e) None of these
82. The feedback component
nent of a differentiator is a _____.
a) Resistor
b) Capacitor
c) Inductor
d) Diode
e) None of these
 ANSWERS .

UNIT-1
1 c 7 b 13 b 19 a
2 a 8 a, b, c, d 14 c. d 20 b 26 c, d
3 a 9 d 15 d 21 b 27 a
4 c 10 b 16 b, d 21 b 28 d
5 a, b, c 11 c 17 c 23 b, c 29 b, d
6 d 12 c 18 a 24 d 30 b
UNIT-2
31 c 37 b, c 43 b 49 c 55 b, c
32 a 38 d 44 a, b 50 d 56 a, b
33 d 39 a 45 d 51 a 57 b, c
34 b 40 d 46 b 52 b 58 b
35 b 41 a, b 47 d 53 c 59 b
36 c 42 b 48 c 54 b 60 a
UNIT-3
61 c 67 a 73 b 79 b
62 d 68 a 74 b 80 d
63 b 69 d 75 d 81 d
64 a 70 c 76 d 82 a
65 d 71 a 77 c
66 a 72 c 78 e