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[MCQ] Electronic Devices and Circuits – II
Module 01
1. When the drain voltage in an n-MOSFET is negative, it is operating in
a. active region
b. inactive region
c. ohmic region
d. reactive region
Answer. b
2. The regions of operation of a MOSFET to work as a linear resistor and linear amplifier are
a. cut-off and saturation respectively
b. triode and cut-off respectively
c. triode and saturation respectively
d. saturation and triode respectively
Answer. c
3. Two MOSFETs M[1] and M[2] are connected in parallel to carry a total current of 20A. The drain to source voltage of M[1] is 2.5V and that of M[2] is 3V. What are the drain currents of M[1] and M[2] when the current sharing series resistances are each of 0.5Ω?
a. 10.5 A and 9.5 A
b. 9.5 A and 10.5 A
c. 10.5 A and 10.5 A
d. 9.5 A and 9.5 A
Answer. a
4. The lower turn off time of MOSFET when compared to BJT can be attributed to which one of the following?
a. input impedance
b. positive temperature coefficient
c. absence of minority carriers
d. on-state resistance
Answer. c
5. What is the main difference between MOSFETs and BJTs in terms of their I-V characteristics?
a. current is quadratic with V[GS] for MOSFETs and linear with V[BE] for BJTs
bb. current is linear with V[GS] for MOSFETs and exponential with V[BE] for BJTs
c. current is exponential with V[GS]/V[BE] in both these devices, but rise is faster in MOSFETs
d. current is quadratic with V[GS] for MOSFETs and exponential with V[BE] for BJTs
Answer. d
6. The modified work function of an n-channel MOSFET is -0.85 V. If the interface charge is 3 × 10^-4 C/m^2 and the oxide capacitance is 300 μF/m^2, the flat band voltage is
a. -1.85 V
b. -0.15 V
c. +0.15 V
d. +1.85 V
Answer. d
7. Enhancement mode is connected with which one of the following?
a. tunnel diode
b. MOSFET
c. photodiode
d. varactor diode
Answer. b
8. The MOSFET switch in its on-state may be considered equivalent to
a. resistor
b. capacitor
c. inductor
d. battery
Answer. b
9. Which of the following pair is not correctly matched?
a. MOSFET – unipolar device
b. BJT – switching power loss
c. MOSFET – high ON state conduction power loss
d. IGBT – voltage-controlled device
Answer. b
10. Identify the incorrect statement regarding power MOSFET.
a. these are so constructed as to avoid punch through
b. the channel length is relatively large and the channel width is relatively small
c. these do not experience any minority charge carrier storage
d. these can be put in parallel to handle large currents
Answer. b
11. An E-MOSFET with its gate connected to its drain is an example of
a. a three-terminal device
b. an active load
c. a passive load
d. a switching device
Answer. b
12. Which of the following devices revolutionised the computer industry?
a. JFET
b. D-MOSFET
c. E-MOSFET
d. Power FET
Answer. c
13. A D-MOSFET can operate in the
a. depletion mode only
b. enhancement mode only
c. depletion mode or enhancement mode
d. low impedance mode
Answer. c
14. For operation of depletion type MOSFET the gate voltage is kept
a. positive
b. highly positive
c. zero
d. negative
Answer. d
15. A MOSFET can be used as
a. resistor
b. capacitor
c. switch
d. all the above
Answer. d
16. Most commonly used insulating layer material for MOSFET is
a. GeO[2]
b. Al[2]O[3]
c. As[2]O[5]
d. SiO[2]
Answer. d
17. Dynamic memory cells are constructed using
a. transistors
b. flip-flops
c. MOSFETs
d. FETs
Answer. c
18. MOSFET can be used as
a. current controlled capacitor
b. voltage controlled capacitor
c. current controlled inductor
d. voltage controlled inductor
Answer. b
19. Which of the following parameters are affected due to short channel MOSFET geometry
i.mobility of carriers
ii.threshold voltage
iii.drain current
a. only i
b. only ii
c. both i and iii
d. i, ii and iii
Answer. d
20. Which of the following characterisitics does an active loaded MOS differential circuit possess?
a. high CMRR
b. low CMRR
c. high delay
d. high differential gain
Answer. d
21. The MOSFET combines the areas of _______ & _________
a) field effect & MOS technology
b) semiconductor & TTL
c) mos technology & CMOS technology
d) none of the mentioned
Answer: a
Explanation: It is an enhancement of the FET devices (field effect) using MOS technology.
22. Which of the following terminals does not belong to the MOSFET?
a) Drain
b) Gate
c) Base
d) Source
Answer: c
Explanation: MOSFET is a three terminal device D, G & S.
23. Choose the correct statement
a) MOSFET is a uncontrolled device
b) MOSFET is a voltage controlled device
c) MOSFET is a current controlled device
d) MOSFET is a temperature controlled device
Answer: b
Explanation: It is a voltage controlled device.
24. Choose the correct statement(s)
i) The gate circuit impedance of MOSFET is higher than that of a BJT
ii) The gate circuit impedance of MOSFET is lower than that of a BJT
iii) The MOSFET has higher switching losses than that of a BJT
iv) The MOSFET has lower switching losses than that of a BJT
a) Both i & ii
b) Both ii & iv
c) Both i & iv
d) Only ii
Answer: c
Explanation: MOSFET requires gate signals with lower amplitude as compared to BJTs & has lower switching losses.
25. Choose the correct statement
a) MOSFET is a unipolar, voltage controlled, two terminal device
b) MOSFET is a bipolar, current controlled, three terminal device
c) MOSFET is a unipolar, voltage controlled, three terminal device
d) MOSFET is a bipolar, current controlled, two terminal device
Answer: c
Explanation: MOSFET is a three terminal device, Gate, source & drain. It is voltage controlled unlike the BJT & only electron current flows.
26. The arrow on the symbol of MOSFET indicates
a) that it is a N-channel MOSFET
b) the direction of electrons
c) the direction of conventional current flow
d) that it is a P-channel MOSFET
Answer: b
Explanation: The arrow is to indicate the direction of electrons (opposite to the direction of conventional current flow).
27. The controlling parameter in MOSFET is
a) Vds
b) Ig
c) Vgs
d) Is
Answer: b
Explanation: The gate to source voltage is the controlling parameter in a MOSFET.
28. In the internal structure of a MOSFET, a parasitic BJT exists between the
a) source & gate terminals
b) source & drain terminals
c) drain & gate terminals
d) there is no parasitic BJT in MOSFET
Answer: b
Explanation: Examine the internal structure of a MOSFET, notice the n-p-n structure between the drain & source. A p-channel MOSFET will have a p-n-p structure.
29. In the transfer characteristics of a MOSFET, the threshold voltage is the measure of the
a) minimum voltage to induce a n-channel/p-channel for conduction
b) minimum voltage till which temperature is constant
c) minimum voltage to turn off the device
d) none of the above mentioned is true
Answer: a
Explanation: It is the minimum voltage to induce a n-channel/p-channel which will allow the device to conduct electrically through its length.
30.The output characteristics of a MOSFET, is a plot of
a) Id as a function of Vgs with Vds as a parameter
b) Id as a function of Vds with Vgs as a parameter
c) Ig as a function of Vgs with Vds as a parameter
d) Ig as a function of Vds with Vgs as a parameter
Answer: b
Explanation: It is Id vs Vds which are plotted for different values of Vgs (gate to source voltage).
31. In the output characteristics of a MOSFET with low values of Vds, the value of the on-state resistance is
a) Vds/Ig
b) Vds/Id
c) 0
d) ∞
Answer: b
Explanation: The o/p characteristics Is a plot of Id verses Vds, which for low values of Vds is almost constant. Hence, the on-state resistance is constant & the slop is its constant value.
32. At turn-on the initial delay or turn on delay is the time required for the
a) input inductance to charge to the threshold value
b) input capacitance to charge to the threshold value
c) input inductance to discharge to the threshold value
d) input capacitance to discharge to the threshold value
Answer: b
Explanation: It is the time required for the input capacitance to charge to the threshold value, which depends on the device configuration. The device can start conducting only after this time.
33. Choose the correct statement
a) MOSFET suffers from secondary breakdown problems
b) MOSFET has lower switching losses as compared to other devices
c) MOSFET has high value of on-state resistance as compared to other devices
d) All of the mentioned
Answer: b
Explanation: MOSFET has lower switching losses due to its unipolar nature & less turn off time. All of the other statements are false.
34. Which among the following devices is the most suited for high frequency applications?
a) BJT
b) IGBT
c) MOSFET
d) SCR
Answer: c
Explanation: MOSFET has the least switching losses among the rest of the devices.
35. Choose the correct statement
a) MOSFET has a positive temperature co-efficient
b) MOSFET has a high gate circuit impedance
c) MOSFET is a voltage controlled device
d) All of the mentioned
Answer: d
Explanation: MOSFETs are voltage controlled devices. They have high gate circuit impedance and are PTC devices.
36. Consider an ideal MOSFET. If Vgs = 0V, then Id = ?
a) Zero
b) Maximum
c) Id(on)
d) Idd
Answer: a
Explanation: Gate current = 0 so device is off (ideally).
37. For a MOSFET Vgs=3V, Idss=5A, and Id=2A. Find the pinch of voltage Vp
a) 4.08
b) 8.16
c) 16.32
d) 0V
Answer: b
Explanation: Use Id = Idd x [1-Vgs/Vp]2.
38. How does the MOSFET differ from the JFET?
a) JFET has a p-n junction
b) They are both the same
c) JFET is small in size
d) MOSFET has a base terminal
Answer: a
Explanation: None.
39. The basic advantage of the CMOS technology is that
a) It is easily available
b) It has small size
c) It has lower power consumption
d) It has better switching capabilities
Answer: c
Explanation: Complementary MOS consumes very less power as compared to all the earlier devices.
40. The N-channel MOSFET is considered better than the P-channel MOSFET due to its
a) low noise levels
b) TTL compatibility
c) lower input impedance
d) faster operation
Answer: d
Explanation: The N-channel are faster than the P-channel type.
41. If a MOSFET is to be used in the making of an amplifier then it must work in
a) Cut-off region
b) Triode region
c) Saturation region
d) Both cut-off and triode region can be used
Answer: c
Explanation: Only in the saturation region a MOSFET can operate as an amplifier.
42. For MOSFET is to be used as a switch then it must operate in
a) Cut-off region
b) Triode region
c) Saturation region
d) Both cut-off and triode region can be used
Answer: d
Explanation: In both regions it can perform the task of a switch.
(Q.43 & Q.44) Using the circuit shown below,
43. Determine the conditions in which the MOSFET is operating in the triode region.
i. VGD > Vt (Threshold voltage)
ii. VDS > VOV
iii. ID ∝ (VOV – 0.5VDS)VDS
a) i, ii, and iii are correct
b) i and iii are correct
c) i and ii are correct
d) ii and iii are correct
Answer: b
Explanation: Only the points I and iii are correct and ii is false.
44. Determine the conditions in which the MOSFET is operating in the saturation region
i. VGD > Vt (Threshold voltage)
ii. VDS > VOV
iii. ID ∝ (VOV)2
a) i, ii, and iii are correct
b) i and iii are correct
c) i and ii are correct
d) ii and iii are correct
Answer: d
Explanation: i is false and ii and iii are true.
45. In the saturation region of the MOSFET the saturation current is
a) Independent of the voltage difference between the source and the drain
b) Depends directly on the voltage difference between the source and the drain
c) Depends directly on the overdriving voltage
d) Depends directly on the voltage supplied to the gate terminal
Answer: a
Explanation: Saturation current does not depends on the voltage difference between the source and the drain in the saturation region of a MOSFET.
46. An n-channel MOSFET operating with VOV=0.5V exhibits a linear resistance = 1 kΩ when VDS is very small. What is the value of the device transconductance parameter kn?
a) 2 mA/V2
b) 20 mA/V2
c) 0.2 A/V2
d) 2 A/V2
Answer: a
Explanation: Use the standard mathematical expression to determine the value of kn.
47. An NMOS transistor is operating at the edge of saturation with an overdrive voltage VOV and a drain current ID. If is VOV is doubled, and we must maintain operation at the edge of saturation, what value of drain current results?
a) 0.25ID
b) 0.5ID
c) 2ID
d) 4ID
Answer: c
Explanation: I0 is directly proportional to VOS.
(Q.48-Q.50) Using the circuit below answer the question
48. Which of the following is true for the triode region?
a. VDG > Vtp
b. VSD < VOV
c. ID ∝ VOV
d. None of the mentioned
Answer: d
Explanation: VDG > |Vtp| and VSD < |VOV|.
49. Which of the following is true for the saturation region?
a) VDG ≤ |Vtp|
b) VSD ≤| VOV|
c) VDG < |Vtp|
d) VSD <| VOV|
Answer: a
Explanation: It is a characteristic for the saturation region.
50. The current iD
a) Depends linearly on VOV in the saturation region
b) Depends on the square of VOV in the saturation region
c) Depends inversely on VOV in the triode region
d) None of the mentioned
Answer: b
Explanation: Use the standard mathematical expressions for i0 in different regions.
51. What is the value of Vt for this transistor?
a) 0.7V
b) 0.8V
c) 0.9V
d) 1.0V
Answer: b
Explanation:
52. If the process transconductance parameter is 50μA/V2, what is the MOSFET’s W/L?
a) 25
b) 50
c) 75
d) 100
Answer: a
Explanation:
(Q.53-Q.55) Consider the amplifier below for the case VDD = 5 V, RD = 24 kΩ, (W/L) = 1 mA/V2, and Vt = 1 V.
53. If the amplifier is biased to operate with an overdrive voltage VOV of 0.5 V, find the incremental gain at the bias point.
a) -3 V/V
b) -6 V/V
c) -9 V/V
d) -12 V/V
Answer: d
Explanation:
54. For amplifier biased to operate with an overdrive voltage of 0.5V, and disregarding the distortion caused by the MOSFET’s square-law characteristic, what is the largest amplitude of a sine-wave voltage signal that can be applied at the input while the transistor remains in saturation?
a) 1.61 V
b) 1.5 V
c) 0.11 V
d) 3.11 V
Answer: b
Explanation: Use the standard mathematical formula to obtain the result.
55. For the input signal of 1.5V what is the value of the gain value obtained?
a) -12.24 V/V
b) -12.44 V/V
c) -12.64 V/V
d) -12.84 V/V
Answer: c
Explanation: The amplitude of the output voltage signal that results is approximately equal to Voq – VOB = 2 – 0.61 = 1.39v.
The gain implied by amplitude is
Gain = -1.39/0.11 = -12.64 V/V.
56. Which of the following is the fastest switching device?
a) JEFT
b) Triode
c) MOSFET
d) BJT
Answer: c
Explanation: MOSFET is the fastest switching device among the given four options.
57. Bias point is also referred by the name
a) DC Operating Point
b) Quiescent Point
c) None of the mentioned
d) All of the mentioned
Answer: d
Explanation: Bias point is called dc operating point as the MOSFET functions best at this point. Also since at the bias point no signal component is present it is called quiescent point (he reason why it is represented by the symbol ‘Q’)
(Q.58 –Q.60) Consider the amplifier circuit shown below. The transistor is specified to have Vt = 0.4 V, kn = 0.4 mA/V2, W/L = 10 and λ = 0. Also, let VDD = 1.8V, RD = 17.5kΩ, VGS = 0.6V and vgs = 0V.
8. Find ID.
a) 0.08 mA
b) 0.16 mA
c) 0.4 mA
d) 0.8 mA
Answer: a
Explanation:
59. Find VDS.
a) 0.1V
b) 0.2 V
c) 0.4 V
d) 0.8 V
Answer: c
Explanation:
60. Find Av.
a) -12 V/V
b) -14 V/V
c) -16 V/V
d) -18 V/V
Solution: b
Explanation: Av = – kn Vov RD
= -0.4 * 10 * 0.2 * 17.5
= – 14.4v
Module 02
1. The gain of an amplifier is expressed in db because
A.It is a simple unit
B.Calculations become easy
C.Human ear response is logarithmic
D.None of the above
Answer: Option C
2. Rc coupling is not use to amplify extremely low frequencies because
A.There is considerable power loss
B.There is hum in the output
C.Electrical size of coupling capacitor becomes very large
D.None of the above
Answer: Option C
3.A current ampification of 2000 is a gain of
A.3 db
B.66 db
C.20 db
D.200 db
Answer: Option B
4.If the power level of an amplifier reduces to half, then db gain will fall by .
A.5 db
B.2 db
C.10 db
D.3 db
Answer: Option D
5.The number of stages directly coupled is limited because
A.Changes in temperature cause thermal instability
B.Circuit becomes heavy and costly
C.It becomes difficult to bias the circuit
D.None of the above
Answer: Option A
6.In the initial stages of a multistage amplifier, we use
A.RC coupling
B.Transformer coupling
C.Direct coupling
D.None of the above
Answer: Option A
7. A radio reciver has _________ of amplification .
A.One stage
B.Two stages
C.Three stages
D.More than one stages
Answer: Option D
8.RC coupling is use for __________ amplification.
A.Voltage
B.Current
C.Power
D.None of the above
Answer: Option A
No explanation is given for this question Let’s Discuss on Board
9.Tranformer coupling is used for _________ amplification .
A.Power
B.Voltage
C.Current
D.None of the above
Answer: Option A
No explanation is given for this question Let’s Discuss on Board
10. The lower and the upper cut off frequencies are also called _______ Frequencies
A.Sideband
B.Resonant
C.Half-resonant
D.Half-power
Answer: Option D
11. The upper or lower cutoff frequency is also called ______ Frequency
A.Resonant
B.Sideband
C.3 db
D.None of the above
Answer: Option C
12. The best frequency response is of ________ coupling.
A.RC
B.Transformer
C.Direct
D.None of the above
Answer: Option C
13. 1 db corresponds to ________ change in voltage or current level
A.40%
B.80%
C.20%
D.25%
Answer: Option A
14. In an RC coupled Amplifier, the voltage gain over mid-frequency range ________
A.Changes abruptly with frequency
B.Is constant
C.Changes uniformly with frequency
D.None of the above
Answer: Option B
15. In an RC coupling scheme, the coupling capacitor CC must be large enough ______________
A.To pass d.c. between the stages
B.Not to attenuate the low frequencies
C.To dissipate high power
D.None of the above
Answer: Option B
16. An Advantage of Rc coupling scheme is the _____________
A.Good impedance matching
B.Economy
C.High efficiency
D.None of the above
Answer: Option B
17. When a multistage amplifer is to amplify dc signal, then on must use coupling
A.RC
B.Transformer
C.Direct
D.None of the above
Answer: Option C
18.The power output of an audio system is 18 W. For a person to notice an increase in the output (loudness or sound intensity) of the system, what must the output power be increased to ?
A.2 W
B.6 W
C.68 W
D.None of the above
Answer: Option C
19. A gain of 1000000 in power is expressed by ___________
A.30 db
B.60 db
C.120 db
D.600 db
Answer: Option B
20. A gain of 1000 times in voltage is expressed by ___________
A.60 db
B.30 db
C.120 db
D.600 db
Answer: Option A
21. Which of these are incorrect about Darlington amplifier?
a) It has a high input resistance
b) The output resistance is low
c) It has a unity voltage gain
d) It is a current buffer
Answer: d
Explanation: A Darlington amplifier has a very high input resistance, low output resistance, unity voltage gain and a high current gain. It is a voltage buffer, not a current buffer.
22. In a Darlington pair, the overall β=15000.β1=100. Calculate the collector current for Q2 given base current for Q1 is 20 μA.
a) 300 mA
b) 298 mA
c) 2 mA
d) 200mA
Answer: b
Explanation: IB = 20 μA
IC = β.IB = 15000 x 20μ = 300 mA
IC1 = β1.IB = 100.20μ = 2mA
IC2 = 300 – 2 = 298mA.
23. Darlington amplifier is an emitter follower.
a) True
b) False
Answer: a
Explanation: Darlington pair is an emitter follower circuit, in which a darling pair is used in place of a single
transistor. It also provides a large β as per requirements.
24. Consider a Darlington amplifier. In the self bias network, the biasing resistances are 220kΩ and 400 kΩ. What can be the correct value of input resistance if hfe = 50 and emitter resistance = 10kΩ.
a) 141 kΩ
b) 15 MΩ
c) 20 MΩ
d) 200 kΩ
Answer: a
Explanation: R’ = 220k||400k = 142 kΩ
RI = (1+hfe)2RE = 26MΩ
RI’ = 26M||142k = 141.22 K.
Module 03
1. A radio receiver has …………… of amplification
a. One stage
b. Two stages
c. Three stages
d. More than one stages
Answer : a
2. RC coupling is used for ………………. amplification
a. Voltage
b. Current
c. Power
d. None of the above
Answer : a
3. In an RC coupled amplifier, the voltage gain over mid-frequency range …………….
a. Changes abruptly with frequency
b. Is constant
c. Changes uniformly with frequency
d. None of the above
Answer : b
4. In obtaining the frequency response curve of an amplifier, the …………
a. Amplifier level output is kept constant
b. Amplifier frequency is held constant
c. Generator frequency is held constant
d. Generator output level is held constant
Answer : d
5. An advantage of RC coupling scheme is the ………….
a. Good impedance matching
b. Economy
c. High efficiency
d. None of the above
Answer : b
6. The best frequency response is of ………. coupling
a. RC
b. Transformer
c. Direct
d. None of the above
Answer : c
7. Transformer coupling is used for ………….. amplification
a. Power
b. Voltage
c. Current
d. None of the above
Answer : a
8. In an RC coupling scheme, the coupling capacitor CC must be large enough ………..
a. To pass d.c. between the stages
b. Not to attenuate the low frequencies
c. To dissipate high power
d. None of the above
Answer : b
9. In RC coupling, the value of coupling capacitor is about ……….
a. 100 pF
b. 0.1 µF
c. 0.01 µF
d. 10 µF
Answer : d
10. The noise factor of an ideal amplifier expressed in db is …………..
a. 0
b. 1
c. 1
d. 10
Answer : a
11. When a multistage amplifier is to amplify d.c. signal, then one must use …….. coupling
a. RC
b. Transformer
c. Direct
d. None of the above
Answer : c
12. ………….. coupling provides the maximum voltage gain
a. RC
b. Transformer
c. Direct
d. Impedance
Answer : b
13. In practice, voltage gain is expressed ……………
a. In db
b. In volts
c. As a number
d. None of the above
Answer : a
14. Transformer coupling provides high efficiency because …………
a. Collector voltage is stepped up
b. c. resistance is low
c. collector voltage is stepped down
d. none of the above
Answer : b
Q15. Transformer coupling is generally employed when load resistance is ………
a. Large
b. Very large
c. Small
d. None of the above
Answer : c
16. If a three-stage amplifier has individual stage gains of 10 db, 5 db and 12 db, then total gain in db is ……….
a. 600 db
b. 24 db
c. 14 db
d. 27 db
Answer : d
17. The final stage of a multistage amplifier uses ………………
a. RC coupling
b. Transformer coupling
c. Direct coupling
d. Impedance coupling
Answer : b
18. The ear is not sensitive to ………….
a. Frequency distortion
b. Amplitude distortion
c. Frequency as well as amplitude distortion
d. None of the above
Answer : 1
19. RC coupling is not used to amplify extremely low frequencies because ………
a. There is considerable power loss
b. There is hum in the output
c. Electrical size of coupling capacitor becomes very large
d. None of the above
Answer : c
20. In transistor amplifiers, we use ……………. transformer for impedance matching
a. Step up
b. Step down
c. Same turn ratio
d. None of the above
Answer : b
21. The lower and upper cut off frequencies are also called ………………… frequencies
a. Sideband
b. Resonant
c. Half-resonant
d. Half-power
Answer : d
22. A gain of 1,000,000 times in power is expressed by …………….
a. 30 db
b. 60 db
c. 120 db
d. 600 db
Answer : b
23. A gain of 1000 times in voltage is expressed by …………..
a. 60 db
b. 30 db
c. 120 db
d. 600 db
Answer : a
24. 1 db corresponds to ………….. change in power level
a. 50%
b. 35%
c. 26%
d. 22%
Answer : c
25. 1 db corresponds to …………. change in voltage or current level
a. 40%
b. 80%
c. 20%
d. 25%
Answer : a
26. The frequency response of transformer coupling is ………….
a. Good
b. Very good
c. Excellent
d. Poor
Answer : d
27. In the initial stages of a multistage amplifier, we use ………..
a. RC coupling
b. Transformer coupling
c. Direct coupling
d. None of the above
Answer : a
28. The total gain of a multistage amplifier is less than the product of the gains of individual stages due to …………
a. Power loss in the coupling device
b. Loading effect of the next stage
c. The use of many transistors
d. The use of many capacitors
Answer : b
29. The gain of an amplifier is expressed in db because ………..
a. It is a simple unit
b. Calculations become easy
c. Human ear response is logarithmic
d. None of the above
Answer : c
30. If the power level of an amplifier reduces to half, the db gain will fall by …….
a. 5 db
b. 2 db
c. 10 db
d. 3 db
Answer : d
31. A current amplification of 2000 is a gain of …………….
a. 3 db
b. 66 db
c. 20 db
d. 200 db
Answer : b
32. An amplifier receives 0.1 W of input signal and delivers 15 W of signal power. What is the power gain in db?
a. 8 db
b. 6 db
c. 5 db
d. 4 db
Answer : a
33. The power output of an audio system is 18 W. For a person to notice an increase in the output (loudness or sound intensity) of the system, what must the output power be increased to ?
a. 2 W
b. 6 W
c. 68 W
d. None of the above
Answer : c
34. The output of a microphone is rated at -52 db. The reference level is 1V under specified conditions. What is the output voltage of this microphone under the same sound conditions?
a. 5 mV
b. 2 mV
c. 8 mV
d. 5 mV
Answer : d
35. RC coupling is generally confined to low power applications because of ………
a. Large value of coupling capacitor
b. Low efficiency
c. Large number of components
d. None of the above
Answer : b
36. The number of stages that can be directly coupled is limited because ……..
a. Changes in temperature cause thermal instability
b. Circuit becomes heavy and costly
c. It becomes difficult to bias the circuit
d. None of the above
Answer : a
37. The purpose of RC or transformer coupling is to …………
a. Block a.c.
b. Separate bias of one stage from another
c. Increase thermal stability
d. None of the above
Answer : b
38. The upper or lower cut off frequency is also called ………….. frequency
a. Resonant
b. Sideband
c. 3 db
d. None of the above
Answer : c
39. The bandwidth of a single stage amplifier is …………. that of a multistage amplifier
a. More than
b. The same as
c. Less than
d. Data insufficient
Answer : a
40. The value of emitter capacitor CE in a multistage amplifier is about ……..
a. 1 µF
b. 100 pF
c. 0.01 µF
d. 50 µF
Answer : d
Module 04
1. Why do we use CE amplifier as a large signal class a amplifier?
a) It has very high output impedance
b) It has very high input impedance
c) It has very high voltage gain
d) It is very much stable
Answer: c
Explanation: Since CE amplifier has reasonably high voltage gain and hence can work with high voltage or large signals.
2. What does class A amplifier do?
a) Delivers KV of voltage to load
b) Delivers KW of power
c) Delivers Kilo Pascal pressure
d) Delivers more resistance
Answer: b
Explanation: Class A always delivers more power to load because of a larger current delivered from the transistor.
3. What is the efficiency of Class A amplifiers?
a) 30 or less
b) 50 or less
c) 100
d) 75
Answer: a
Explanation: Since in Class A amplifiers distortion is more and as it requires tuned circuit as load, the efficiency is very low.
4. An ideal large signal amplifier delivers 100% DC power to its load.
a) True
b) False
Answer: a
Explanation: In an ideal case, no distortion occurs, that is noise effects are completely ignored, hence it gives 100% efficiency.
5. Which of the following statement is true about class A amplifiers?
a) They are weak against distortions
b) They supress noise signals
c) More efficient
d) Delivers 100% power to load
Answer: a
Explanation: Since class A amplifiers use basic transistor, even the noise signal will get amplified when the noise signal exists in input.
6. Why there is a need for heat sinks in Class A amplifier?
a) To control the external temperature
b) To avoid temperature changes affecting the transistor
c) To control heat dissipation
d) To increase output resistance
Answer: c
Explanation: When even no input is given to class A amplifiers, it produces some current to load, and hence heat sinks are required to avoid this.
7. Basic operation of Class A amplifiers____________
a) Crossover distortion
b) Law of Conservation of energy
c) Millers law
d) Switching transistor theory
Answer: d
Explanation: The class A amplifier is the simplest form of power amplifier that uses the switching transistor in the standard common emitter configuration.
8. If DC power for a Class A amplifier is 500W and AC power is 150W, what is its efficiency?
a) 50%
b) 75%
c) 20%
d) 30%
Answer: d
Explanation: efficiency=AC POWER/DC POWER
Efficiency=150/500=3/10
In percentage 3*100/10=30%.
9. Which of the following technique is used to increase the efficiency of class A amplifier?
a) By using FET
b) By using PNP transistor
c) By using matched transformers as load
d) By using potentiometers as load
Answer: c
Explanation: We can increase the efficiency of class A amplifier by using load matching concept, hence a pair of matched transformer can be used as load which in turn increases the efficiency.
10. What is the conduction angle of class A amplifier?
a) 90
b) 180
c) 270
d) 360
Answer: d
Explanation: Since the amplifier is always On, it conducts all the current waveform which can be used to state that it has 360 degree conduction angle.
11. Which of these is not true for a class B amplifier?
a) It has zero DC bias
b) They have an efficiency less than that of class A amplifiers
c) The quiescent power dissipation is zero
d) The conduction angle is only 180°
Answer: b
Explanation: The class B amplifier has zero DC bias as the transistors are biased at cut-off only. Each transistor conducts when the input is greater than the base-emitter voltage. The conduction angle is only 180° for this amplifier. They have higher efficiency than class A amplifiers.
12. What is the output of a class B amplifier for sinusoidal input?
a) Sinusoidal amplifier
b) Half-sinusoidal
c) Sinusoidal with higher frequency
d) Square wave
Answer: b
Explanation: If Q-point is in cut-off, then IC varies only in the positive direction, for saturation, it varies in the negative direction. So the output of Class B amplifier is half sinusoidal. There is no effect in the shape or the frequency of the wave.
13. How do we obtain sinusoidal output out of a class B amplifier?
a) By using non-sinusoidal inputs
b) By utilizing two transistors
c) By biasing it in the active region
d) By adding a capacitor to the output
Answer: b
Explanation: To obtain sinusoidal output from a class B amplifier, two transistors must be used. Such a circuit is a class B push-pull amplifier, used in unturned power amplifiers and audio frequency power amplifiers.
14. In a class B amplifier, it is found that DC power is 25W, find the ac power.
a) 10 W
b) 62.5 W
c) 25 W
d) 50 W
Answer: b
Explanation: For a class B amplifier, figure of merit = 0.4 = dc power/ac power
Thus AC power = DC power/0.4 = 25/0.4 = 62.5 W.
15. When is the maximum efficiency of class B amplifier achieved?
a) When VMAX = VCC
b) When two transistors are used
c) When VMIN = 0
d) Efficiency is always constant
Answer: c
Explanation: Efficiency % = [1-VMIN/VCC] x 78.5
Maximum efficiency occurs when VMIN=0 and efficiency is 78.5%.
16. What is the disadvantage of a class B push-pull amplifier?
a) The efficiency reduces
b) The figure of merit increases
c) The cross-over distortion occurs
d) The Q-power dissipation is very large
Answer: c
Explanation: A class B amplifier helps increase efficiency, and the figure of merit reduces. The q power dissipation reduces and cross over distortion increases. Due to two transistors, when one transistor turns off the other does not begin conduction immediately, hence output current is zero for a short interval.
17. Read statements and select the correct option below.
A: A push-pull amplifier decreases harmonic distortion
B: Output has half-wave symmetry
a) A and B are both correct and B is the correct reason for A
b) A is correct and B is incorrect
c) Both A and B are correct but B is not the correct reason for A
d) Both A and B are incorrect
Answer: c
Explanation: A push-pull amplifier reduced harmonic distortion as it cancels even harmonic frequencies. Net current in load I=K(I1-I2)
Due to this, even harmonics cancel out and decrease harmonic distortion. Thus output has half-wave symmetry.
18. Why does no DC current flow in the primary winding of the output transformer of class B push-pull amplifier?
a) Because DC currents from both transistors flow in opposite directions
b) Because the net impedance is very high to allow flow of current
c) The winding only allows AC current to flow
d) Current only flows in secondary winding due to the presence of load at that side
Answer: a
Explanation: The net DC current in the primary winding of the output transformer is zero because DC collector currents of both transistors being used flow in opposite directions and hence transformer saturation doesn’t occur.
19. Which of these is incorrect for complementary symmetry push-pull amplifiers?
a) During positive cycle NPN transistor conducts
b) It is easier to fabricate on IC
c) Size of the transformer required reduces
d) Efficiency and figure of merit are same as transformer coupled push-pull amplifier
Answer: c
Explanation: The complementary symmetry push-pull amplifier uses one NPN and one PNP transistor to conduct in positive and negative cycles respectively. It does not affect efficiency or figure of merit, but since no transformer is being used, it is easier to fabricate on ICs.
20. The maximum a.c. power output from a class A power amplifier is 10 W. What should be the minimum power rating of the transistor used ?
a. 10 W
b. 15 W
c. 5 W
d. 20 W
Answer : d
21. The output stage of a multistage amplifier is also called ……………
a. Mixer stage
b. Power stage
d. Detector stage
d. F stage
Answer : b
22. ………………. coupling is generally employed in power amplifiers
a. Transformer
b. RC
c. direct
d. Impedance
Answer : a
23. A class A power amplifier uses …………
a. Two transistors
b. Three transistors
c. One transistor
d. None of the above
Answer : c
24. The maximum efficiency of resistance loaded class A power amplifier is ……..
a. 5%
b. 50%
c. 30%
d. 25%
Answer : d
25. The maximum efficiency of transformer coupled class A power amplifier is ………………
a. 30%
b. 50%
c. 80%
d. 45%
Answer : b
26. Class……. power amplifier has the highest collector efficiency
a. C
b. A
c. B
d. AB
Answer : a
27. Power amplifiers handle …………. signals compare to voltage amplifiers
a. Small
b. Very small
c. Large
d. None of the above
Answer : c
28. In class A operation, the operating point is generally located ………. of the d.c. load line.
a. At cut off point
b. At the middle
c. At saturation point
d. None of the above
Answer : b
29. Class C amplifiers are used as …………….
a. AF amplifiers
b. Detectors
c. F. amplifiers
d. None of the above
Answer : c
30. A power amplifier has comparatively …………….. β
a. Small
b. Large
c. Very large
d. None of the above
Answer : a
31. The maximum collector efficiency of class B operation is ……………..
a. 50%
b. 90%
c. 5%
d. 5%
Answer : d
32. A 2-transistor class B power amplifier is commonly called ……….. amplifier
a. Dual
b. Push-pull
c. Symmetrical
d. Differential
Answer : b
33. If a transistor is operated in such a way that output current flows for 60o of the input signal, then it is …………… operation
a. Class A
b. Class B
c. Class C
d. None of the above
Answer : c
34. If the zero signal dissipation of a transistor is 1W, then power rating of the transistor should be at least ……………….
a. 5 W
b. 33 W
c. 75 W
d. 1 W
Answer : d
35. When a transistor is cut off……………..
a. Maximum voltage appears across transistor
b. Maximum current flows
c. Maximum voltage appears across load
d. None of the above
Answer : a
36. A class A power amplifier is sometimes called ………….. amplifier
a. Symmetrical
b. Single-ended
c. Reciprocating
d. Differential
Answer : b
37. Class ………….. operation gives the maximum distortion
a. A
b. B
c. C
d. AB
Answer : c
38. The output stage of a multistage amplifier usually employs ………..
a. Push-pull amplifier
b. Preamplifier
c. Class A power amplifier
d.None of the above
Answer : a
39. The size of a power transistor is made considerably large to …………
a. Provide easy handling
b. Dissipate heat
c. Facilitate connections
d. None of the above
Answer : b
40. Low efficiency of a power amplifier results in ……………….
a. Low forward bias
b. Less battery consumption
c. More battery consumption
d. None of the above
Answer : c
41. The driver stage usually employs………….
a. Class A power amplifier
b.Push-pull amplifier
c. Class C amplifier
d. None of the above
Answer : a
42. If the power rating of a transistor is 1W and collector current is 100mA, then maximum allowable collector voltage is ………..
a. 1V
b. 100V
c. 20V
d. 10V
Answer : d
43. When no signal is applied, the approximate collector efficiency of class A power amplifier is …….
a. 10%
b. 0%
c. 25%
d. 50%
Answer : b
44. What will be the collector efficiency of a power amplifier having zero signal power dissipation of 5 watts and a.c. power output of 2 watts?
a. 20%
b. 80%
c.40%
d. 50%
Answer : c
45. The output signal voltage and current of a power amplifier are 5V and 200 mA; the values being r.m.s. What is the power output?
a. 1 W
b. 2 W
c. 4 W
d. None of the above
Answer : a
Module 05
1. Open-loop gain of an amplifier is given by:
a. A
b. Aβ
c. β
d. None of the above
answer: A. A
2. Loop gain is given by:
a. A
b. Aβ
c. β
d. None of the above
answer: B. Aβ
3. In a feedback amplifier, sensitivity D is equal to:
a. Aβ
b. 1 – Aβ
c. 1 + Aβ
d. 1/(Aβ + 1)
answer: C. 1 + Aβ
4. In a negative feedback amplifier, voltage sampling:
a. Tends to decrease the output resistance
b. Tends to increase to output resistance
c. Does not alter the output resistance
d. Produces the same effect on output resistance as current sampling
answer:B. Tends to increase to output resistance
5. In a negative feedback amplifier, current sampling:
a. Tends to increase the output resistance
b. Tends to decrease the output resistance
c. Does not alter the output resistance
d. Produces the same effect on input resistance as voltage sampling
answer: B. Tends to decrease the output resistance
6. In a negative feedback amplifier, series mixing:
a. Tends to increase the input resistance
b. Tends to decrease the input resistance
c. Does not alter the input resistance
d. Produces the same effect on input resistance as shunt mixing
answer: A. Tends to increase the input resistance
7. In a negative feedback amplifier, shunt mixing:
a. Tends to increase the input resistance
b. Tends to decrease the input resistance
c. Does not alter the input resistance
d. Produces the same effect on input resistance as the series mixing
answer: B. Tends to decrease the input resistance
8. Negative feed back in an amplifier improves:
a. The signal to noise ratio at the output
b. Reduces distortion
c. Both (a) and (b)
d. None of the above
answer: C. Both (a) and (b)
9. For a shunt-shunt negative feedback amplifier
s. Input impedance decreases but output impedance increases
b. Both input impedance and output impedance increases
c. Both input impedance and output impedance decreases
d. None of the above
A. Input impedance decreases but output impedance increases
10. An amplifier with the negative feedback:
a. Controls the gain
b. Reduces the noise
c. Reduces phase distortion
d. All of the above
answer: D. All of the above
11. An amplifier with resistive negative feedback has two left half plane poles in its open-loop transfer junction. The amplifier will be:
a. Stable for all frequencies
b. Unstable for all frequency
c. Stable for a particular frequencies
d. Unstable for a particular frequencies
answer: A. Stable for all frequencies
12. Barkhusen criteria is:
a. Positive feedback, Aβ = 1, θ = 0 or multiple 360
b. Negative feedback, Aβ = 1, θ = 0 or multiple 360
c. Positive feedback, Aβ = 0, θ = 0 or multiple 360
d. Negative feedback, Aβ = 1, θ = 180
answer: A. Positive feedback, Aβ = 1, θ = 0 or multiple 360
13. The negative feedback in an amplifier
a. Increase the voltage gain
b. Decrease the voltage gain
c. Stabilize the voltage gain
d. B and C both are correct
answer:D. B and C both are correct
14. One of the effects of negative feedback in amplifier is to
a. Increase the noise
b. Decrease the harmonic distortion
c. Increase the voltage gain
d. Decrease the bandwidth
answer: B. Decrease the harmonic distortion
15. An emitter follower circuit is widely used in electric instruments because
a. Its voltage gain is very high
b. Its voltage gain is less than 1
c. Input impedance is high and output impedance is low
d. It employees no bypass capacitor
answer: C. Input impedance is high and output impedance is low
16. Negative feedback in amplifier
a. Increase the gain stability
b. Decrease distortion and noise level
c. Increase input impedance and decreases output impedance
d. All of these
answer:D. All of these
17. The input impedance of an amplifier can be increased from 2 kilo ohm 250 Kohm by introducing
a. Shunt current negative feedback
b. Shunt voltage negative feedback
c. Series current negative feedback
d. None of thes
C. Series current negative feedback
18. The what is gain of an amplifier is 100, when negative feedback with m=0.04 is introduced, it’s been will be
a. 20
b. 25
c. 4
d. 0.4
answer:A. 20
19. With negative feedback, the returning signal
a. Aids the input signal
b. Opposes the input signal
c. Is proportional to output current
d. Is proportional to differential voltage gain
answer: B. Opposes the input signal
20. How many types of negative feedback are there?
a. One
b. Two
c. Three
d. Four
answer:D. Four
21. A VCVS amplifier approximates an ideal
a. Voltage amplifier
b. Current-to-voltage converter
c. Current-to-voltage converter
d. Current amplifier
answer: A. Voltage amplifier
22. The voltage between the input terminals of an ideal op amp is
a. Zero
b. Very small
c. Very large
d. Equal to the input voltage
answer: A. Zero
23. When an op amp is not saturated, the voltages at the non-inverting and inverting inputs are
a. Almost equal
b. Much different
c. Equal to the output voltage
d. Equal to +15 V
answer: A. Almost equal
24. The feedback fraction B
a. Is always less than 1
b. Is usually greater than 1
c. May equal 1
d. May not equal 1
answer:C. May equal 1
25. An ICVS amplifier has no output voltage. A possible trouble is
a. No negative supply voltage
b. Shorted feedback resistor
c. No feedback voltage
d. Open load resistor
answer:B. Shorted feedback resistor
26. In a VCVS amplifier, any decrease in open-loop voltage gain produces an increase in
a. Output voltage
b. Error voltage
c. Feedback voltage
d. Input voltage
answer: B. Error voltage
27. The open-loop voltage gain equals the
a. Gain with negative feedback
b. Differential voltage gain of the op amp
c. Gain when B is 1
d. Gain at funity
answer:B. Differential voltage gain of the op amp
28. The loop gain AOLB
a. Is usually much smaller than 1
b. Is usually much greater than 1
c. May not equal 1
d. Is between 0 and 1
answer: B. Is usually much greater than 1
29. The closed-loop input impedance with an ICVS amplifier is
a. Usually larger than the open-loop input impedance
b. Equal to the open-loop input impedance
c. Sometimes less than the open-loop impedance
d. Ideally zero
answer:D. Ideally zero
30. With an ICVS amplifier, the circuit approximates an ideal
a. Voltage amplifier
b. Current-to-voltage converter
c. Voltage-to-current converter
d. Current amplifier
answer: B. Current-to-voltage converter
31. When negative voltage feedback is applied to an amplifier, its voltage gain ……………….
a. Is increased
b. Is reduced
c. Remains the same
d. None of the above
Answer : b
32. The value of negative feedback fraction is always …………….
a. Less than 1
b. More than 1
c. Equal to 1
d. None of the above
Answer : a
33. If the output of an amplifier is 10 V and 100 mV from the output is fed back to the input, then feedback fraction is ………..
a. 10
b. 1
c. 01
d. 15
Answer : c
34. The gain of an amplifier without feedback is 100 db. If a negative feedback of 3 db is applied, the gain of the amplifier will become …………..
a. 5 db
b. 300 db
c. 103 db
d. 97 db
Answer : d
35. If the feedback fraction of an amplifier is 0.01, then voltage gain with negative feedback is approximately………..
a. 500
b. 100
c. 1000
d. 5000
Answer : b
36. A feedback circuit usually employs ……………… network
a. Resistive
b. Capacitive
c. Inductive
d. None of the above
Answer : a
37. The gain of an amplifier with feedback is known as ………….. gain
a. Resonant
b. Open loop
c. Closed loop
d. None of the above
Answer : c
38. When voltage feedback (negative) is applied to an amplifier, its input impedance ………….
a. Is decreased
b. Is increased
c. Remains the same
d. None of the above
Answer : b
39. When current feedback (negative) is applied to an amplifier, its input impedance …………..
a. Is decreased
b. Is increased
c. Remains the same
d. None of the above
Answer : a
40. Negative feedback is employed in ……………..
a. Oscillators
b. Rectifiers
c. Amplifiers
d. None of the above
Answer : c
41. Emitter follower is used for …………
a. Current gain
b. Impedance matching
c. Voltage gain
d. None of the above
Answer : b
42. The voltage gain of an emitter follower is ………..
a. Much less than 1
b. Approximately equal to 1
c. Greater than 1
d. None of the above
Answer : b
43. When current feedback (negative) is applied to an amplifier, its output impedance ……..
a. Is increased
b. Is decreased
c. Remains the same
d. None of the above
Answer : a
44. Emitter follower is a ……………….. circuit
a. Voltage feedback
b. Current feedback
c. Both voltage and current feedback
d. None of the above
Answer : b
45. If voltage feedback (negative) is applied to an amplifier, its output impedance …………..
a. Remains the same
b. Is increased
c. Is decreased
d. None of the above
Answer : c
46. When a negative voltage feedback is applied to an amplifier, its bandwidth……….
a. Is increased
b. Is decreased
c. Remains the same
d. Insufficient data
Answer : a
47. An emitter follower has ………… input impedance
a. Zero
b. Low
c. High
d. None of the above
Answer : c
48. The output impedance of an emitter follower is ……….
a. High
b. Very high
c. Almost zero
d. Low
Answer : d
49. An ICVS amplifier is saturated. A possible trouble is
a. No supply voltages
b. Open feedback resistor
c. No input voltage
d. Open load resistor
answer: B. Open feedback resistor
50. A VCVS amplifier has no output voltage. A possible trouble is
a. Shorted load resistor
b. Open feedback resistor
c. Excessive input voltage
d. Open load resistor
answer: A. Shorted load resistor
Module 06
1. Which is the necessary condition of gain while designing RC phase shift oscillator in order to ensure the sustained oscillations?
a. A ≥ 29
b. A ≤ 29
c. A ≠ 29
d. None of the above
ANSWER: A ≥ 29
2. Which among the following parameters acts as an initiator for the operation of an oscillator in the absence of input signal?
a. Noise voltage
b. Noise power
c. Noise temperature
d. Noise figure
ANSWER: Noise voltage
3. Why is the practical value of | Aβ | considered or adjusted to be slightly greater than ‘1’?
a. To compensate for noise voltage
b. To compensate for phase shifting of two relevant signals upto 180°
c. To compensate for non-linearities existing in the circuit
d. To compensate for the change in feedback voltage
ANSWER: To compensate for non-linearities existing in the circuit
4. Multivibrators belong to the category of _____________
a. Square wave oscillators
b. Triangular wave oscillators
c. Ramp wave oscillators
d. Sinusoidal oscillators
ANSWER: Square wave oscillators
5. Which among the following does not belong to the category of LC oscillators?
a. Hartley oscillator
b. Colpitt’s oscillator
c. Clapp oscillator
d. Wein bridge oscillator
ANSWER: Wein bridge oscillator
6. Which among the below mentioned oscillators does not adopt any kind of feedback mechanism?
a. Phase-shift oscillator
b. Wein bridge oscillator
c. UJT relaxation oscillator
d. All of the above
Answer Explanation
ANSWER: UJT relaxation oscillator
7. What is an angle of phase shift for each designed RC network in the Phase Shift Oscillator circuit?
a. 30°
b. 60°
c. 90°
d. 180°
ANSWER: 60°
8. Which among the following components is /are not involved in the feedback network configuration of LC oscillators?
a. Inductor
b. Capacitor
c. Resistor
d. All of the above
ANSWER: Resistor
9. According to the property of tuned circuit used in LC oscillators, the decay rate is proportional to________
a. Shape & size of current pulse
b. Time constant
c. Both a and b
d. None of the above
ANSWER: Time constant
10. Which among the following measures is/are adopted/used for improving the frequency stability in Colpitt’s oscillator?
a. Clapp oscillator
b. Temperature stabilized chamber
c. Voltage regulators
d. All of the above
ANSWER: All of the above
11. Which among the following oscillators are specifically preferred at high frequencies?
a. LC oscillators
b. RC oscillator
c. Both a and b
d. None of the above
ANSWER: LC oscillators
12. ………….. oscillator incorporates two interdependent circuits in such a way that the output of each controls the input of the other
A.Feedback
B.Sine wave
C.Relaxation
D.Low impedance
Answer: C.Relaxation
13. The phase shift oscillator generally contains
A.Four stages of RC circuit
B.One stage of LC circuit
C.Three stages of RC circuit
D.Two stages of RC circuit
Answer: C.Three stages of RC circuit
14. The oscillator that is mostly used for generating signals of frequency of few ‘MHz’ is
A.Armstrong oscillator
B.Crystal oscillator
C.Wein bridge oscillator
D.Colpitts oscillator
Answer: D.Colpitts oscillator
15. The fundamental requirement for oscillations in an amplifier is
A.Positive feedback from output to input
B.Ample power gain of the amplifier
C.Negative feedback from output to input
D.None of the above
Answer: A.Positive feedback from output to input
16. Which of the following is a stable sine-wave audio-generator?
A.Wein-bridge oscillator
B.Hartley oscillator
C.Armstrong oscillator
D.None of the above
Answer: A.Wein-bridge oscillator
17. An oscillator converts ……………..
a. c. power into d.c. power
b. c. power into a.c. power
c. mechanical power into a.c. power
d. none of the above
Answer : b
18. In an LC transistor oscillator, the active device is ……………
a. LC tank circuit
b. Biasing circuit
c. Transistor
d. None of the above
Answer : c
19. In an LC circuit, when the capacitor is maximum, the inductor energy is ……….
1. Minimum
2. Maximum
3. Half-way between maximum and minimum
4. None of the above
Answer : a
20. In an LC oscillator, the frequency of oscillator is ……………. L or C.
a. Proportional to square of
b. Directly proportional to
c. Independent of the values of
d. Inversely proportional to square root of
Answer : d
21. An oscillator produces……………. oscillations
a. Damped
b. Undamped
c. Modulated
d. None of the above
Answer : d
22. An oscillator employs ……………… feedback
a. Positive
b. Negative
c. Neither positive nor negative
d. Data insufficient
Answer : a
23. An LC oscillator cannot be used to produce ……………….. frequencies
a. High
b. Audio
c. Very low
d. Very high
Answer : c
24. Hartley oscillator is commonly used in ………………
a. Radio receivers
b. Radio transmitters
c. TV receivers
d. None of the above
Answer : a
25. In a phase shift oscillator, we use …………. RC sections
a. Two
b. Three
c. Four
d. None of the above
Answer : b
26. In a phase shift oscillator, the frequency determining elements are …………
a. L and C
b. R, L and C
c. R and C
d. None of the above
Answer : c
27. A Wien bridge oscillator uses ……………. feedback
a. Only positive
b. Only negative
c. Both positive and negative
d. None of the above
Answer : c
28. The piezoelectric effect in a crystal is ……………
a. A voltage developed because of mechanical stress
b. A change in resistance because of temperature
c. A change in frequency because of temperature
d. None of the above
Answer : a
29. If the crystal frequency changes with temperature, we say that crystal has ………….. temperature coefficient
a. Positive
b. Zero
c. Negative
d.. None of the above
Answer : a
30. The crystal oscillator frequency is very stable due to ………………. of the crystal
a. Rigidity
b. Vibrations
c. Low Q
d. High Q
Answer : d
31. The application where one would most likely find a crystal oscillator is ……………..
a. Radio receiver
b. Radio transmitter
c. AF sweep generator
d. None of the above
Answer : b
32. An oscillator differs from an amplifier because it ………
a. Has more gain
b. Requires no input signal
c. Requires no d.c. supply
d. Always has the same input
Answer : b
33. One condition for oscillation is ………….
a. A phase shift around the feedback loop of 180^o
b. A gain around the feedback loop of one-third
c. A phase shift around the feedback loop of 0^o
d. A gain around the feedback loop of less than 1
Answer : c
34. A second condition for oscillations is ……………….
a. A gain of 1 around the feedback loop
b. No gain around the feedback loop
c. The attention of the feedback circuit must be one-third
d. The feedback circuit must be capacitive
Answer : a
35. In a certain oscillator A[v] = 50. The attention of the feedback circuit must be …………
a. 1
b. 01
c. 10
d. 02
Answer : d
36. For an oscillator to properly start, the gain around the feedback loop must initially be
a. 1
b. Greater than 1
c. Less than 1
d. Equal to attenuation of feedback circuit
Answer : b
37. In a Wien-bridge oscillator, if the resistances in the positive feedback circuit are decreased, the frequency……….
a. Remains the same
b. Decreases
c. Increases
d.. Insufficient data
Answer : c
38. In Colpitt’s oscillator, feedback is obtained …………….
a. By magnetic induction
b. By a tickler coil
c. From the centre of split capacitors
d. None of the above
Answer : c
39. The Q of the crystal is of the order of …………
a. 100
b. 1000
c. 50
d. More than 10,000
Answer : d
40. Quartz crystal is most commonly used in crystal oscillators because ………….
a. It has superior electrical properties
b. It is easily available
c. It is quite inexpensive
d. None of the above
Answer : a
41. ………….. is a fixed frequency oscillator
a. Phase-shift oscillator
b. Hartely-oscillator
c. Colpitt’s oscillator
d. Crystal oscillator
Answer : d
42. In an LC oscillator, if the value of L is increased four times, the frequency of oscillations is …………
a. Increased 2 times
b. Decreased 4 times
c. Increased 4 times
d. Decreased 2 times
Answer : d
43. An important limitation of a crystal oscillator is ……………
a. Its low output
b. Its high Q
c. Less availability of quartz crystal
d. Its high output
Answer : a
44. The signal generator generally used in the laboratories is ………….. oscillator
a. Wien-bridge
b. Hartely
c. Crystal
d. Phase shift
Answer : a
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