Top 100 MCQs for Analog Electronics

33. Which parameter of an op-amp describes how well it rejects common-mode signals?

• (a) Slew rate
• (b) CMRR
• (c) Bandwidth
• (d) THD
  Answer: (b) CMRR
  Explanation: CMRR (Common-Mode Rejection Ratio) indicates the ability of an op-amp to reject common-mode signals.

34. Which device is used to generate high-frequency signals?

• (a) Diode
• (b) BJT
• (c) Oscillator
• (d) Transformer
  Answer: (c) Oscillator
  Explanation: Oscillators are used to generate continuous high-frequency signals.

35. What happens to the bandwidth if the gain of an amplifier increases?

• (a) Increases
• (b) Decreases
• (c) Remains constant
• (d) Doubles
  Answer: (b) Decreases
  Explanation: In amplifiers, as gain increases, bandwidth typically decreases due to the gain-bandwidth product.

36. Which of the following is an example of a passive filter?

• (a) LC filter
• (b) Op-amp filter
• (c) Transistor filter
• (d) Digital filter
  Answer: (a) LC filter
  Explanation: LC filters are passive as they use inductors and capacitors without requiring external power.

37. What type of waveform is generated by a 555 timer in astable mode?

• (a) Sine wave
• (b) Square wave
• (c) Triangular wave
• (d) Ramp wave
  Answer: (b) Square wave
  Explanation: In astable mode, the 555 timer generates a continuous square wave.

38. What is the primary function of a voltage divider?

• (a) Generate current
• (b) Divide input voltage
• (c) Increase voltage
• (d) Filter signals
  Answer: (b) Divide input voltage
  Explanation: Voltage dividers split input voltage into smaller parts based on resistance ratios.

39. Which transistor configuration has the lowest output impedance?

• (a) Common-emitter
• (b) Common-base
• (c) Common-collector
• (d) Emitter-follower
  Answer: (c) Common-collector
  Explanation: Common-collector configuration offers low output impedance and high current gain.

40. What is the efficiency of a class B amplifier?

• (a) 25%
• (b) 50%
• (c) 78.5%
• (d) 90%
  Answer: (c) 78.5%
  Explanation: Class B amplifiers have a theoretical efficiency of 78.5%.

41. What is the voltage gain of an inverting op-amp with input resistance R1=1 kΩR_1 = 1 \,k\OmegaR1​=1kΩ and feedback resistance Rf=10 kΩR_f = 10 \,k\OmegaRf​=10kΩ?

• (a) -1
• (b) -10
• (c) 10
• (d) 1
  Answer: (b) -10
  Explanation: The voltage gain of an inverting op-amp is Av=−RfR1=−10 kΩ1 kΩ=−10A_v = -\frac{R_f}{R_1} = -\frac{10 \,k\Omega}{1 \,k\Omega} = -10Av​=−R1​Rf​​=−1kΩ10kΩ​=−10.

42. What is the primary function of a rectifier?

• (a) Amplify signals
• (b) Convert AC to DC
• (c) Convert DC to AC
• (d) Filter signals
  Answer: (b) Convert AC to DC
  Explanation: Rectifiers convert alternating current (AC) into direct current (DC).

43. Which type of MOSFET operates with a negative gate-to-source voltage?

• (a) n-channel MOSFET
• (b) p-channel MOSFET
• (c) Enhancement MOSFET
• (d) Schottky MOSFET
  Answer: (b) p-channel MOSFET
  Explanation: A p-channel MOSFET conducts when the gate-to-source voltage is negative.

44. Which feedback topology is used in a voltage amplifier?

• (a) Voltage-series
• (b) Voltage-shunt
• (c) Current-series
• (d) Current-shunt
  Answer: (a) Voltage-series
  Explanation: Voltage-series feedback is used to control the voltage gain of an amplifier.

45. In a crystal oscillator, which component determines the frequency of oscillation?

• (a) Capacitor
• (b) Resistor
• (c) Quartz crystal
• (d) Inductor
  Answer: (c) Quartz crystal
  Explanation: The frequency of oscillation is determined by the resonant frequency of the quartz crystal.

46. Which class of amplifier operates only during a small portion of the input cycle?

• (a) Class A
• (b) Class B
• (c) Class C
• (d) Class D
  Answer: (c) Class C
  Explanation: Class C amplifiers conduct for less than 180° of the input signal.

47. What is the purpose of a phase-locked loop (PLL)?

• (a) Amplify signals
• (b) Modulate signals
• (c) Lock the frequency of the output to the input
• (d) Filter noise
  Answer: (c) Lock the frequency of the output to the input
  Explanation: A PLL ensures the output frequency remains in phase and synchronized with the input signal.

48. Which of the following describes a voltage regulator’s load regulation?

• (a) Output voltage stability for varying input
• (b) Output voltage stability for varying load
• (c) Efficiency at maximum load
• (d) Noise reduction in the circuit
  Answer: (b) Output voltage stability for varying load
  Explanation: Load regulation ensures the output voltage remains constant despite changes in the load.

49. What is the advantage of negative feedback in amplifiers?

• (a) Increases gain
• (b) Increases distortion
• (c) Reduces bandwidth
• (d) Improves stability
  Answer: (d) Improves stability
  Explanation: Negative feedback stabilizes the amplifier, reduces distortion, and increases bandwidth.

50. Which device is used in optocouplers?

• (a) LED
• (b) Photodiode
• (c) Triac
• (d) Both (a) and (b)
  Answer: (d) Both (a) and (b)
  Explanation: Optocouplers use an LED and a photodiode to transfer signals through light without electrical contact.

51. Which amplifier configuration provides maximum voltage gain?

• (a) Common-collector
• (b) Common-emitter
• (c) Common-base
• (d) Emitter-follower
  Answer: (b) Common-emitter
  Explanation: A common-emitter amplifier provides the highest voltage gain among the three transistor configurations.

52. What is the input impedance of an ideal op-amp?

• (a) 0 ohms
• (b) Infinite
• (c) 100 ohms
• (d) 1 MΩ
  Answer: (b) Infinite
  Explanation: An ideal op-amp has infinite input impedance to prevent loading the input source.

53. What type of filter allows signals within a certain frequency range to pass while blocking others?

• (a) Low-pass filter
• (b) High-pass filter
• (c) Band-pass filter
• (d) Band-stop filter
  Answer: (c) Band-pass filter
  Explanation: A band-pass filter passes frequencies within a certain range and attenuates others.

54. In an op-amp, what does the term “slew rate” refer to?

• (a) Gain of the op-amp
• (b) Maximum rate of change of the output voltage
• (c) Input offset voltage
• (d) Open-loop bandwidth
  Answer: (b) Maximum rate of change of the output voltage
  Explanation: The slew rate defines how quickly the output of an op-amp can change in response to an input signal.

55. What is the purpose of the emitter bypass capacitor in a common-emitter amplifier?

• (a) Improve voltage gain
• (b) Reduce power consumption
• (c) Block DC components
• (d) Stabilize the input signal
  Answer: (a) Improve voltage gain
  Explanation: The bypass capacitor shorts the emitter resistor for AC signals, increasing the AC voltage gain.

56. Which type of diode is used in voltage regulation applications?

• (a) Zener diode
• (b) Schottky diode
• (c) Tunnel diode
• (d) LED
  Answer: (a) Zener diode
  Explanation: A Zener diode maintains a constant output voltage despite fluctuations in input voltage or load conditions.

57. Which amplifier provides the highest efficiency?

• (a) Class A
• (b) Class B
• (c) Class C
• (d) Class D
  Answer: (d) Class D
  Explanation: Class D amplifiers, using pulse-width modulation, achieve very high efficiency (often over 90%).

58. What is the significance of the cut-off frequency in a filter?

• (a) The maximum operating frequency
• (b) Frequency at which power drops to half
• (c) Frequency at which the phase becomes 180°
• (d) Frequency at which current is maximum
  Answer: (b) Frequency at which power drops to half
  Explanation: The cut-off frequency marks the point where the output power drops to 50% of the input power (3 dB drop).

59. In a transistor, the region between cut-off and saturation is called:

• (a) Active region
• (b) Breakdown region
• (c) Inversion region
• (d) Quiescent region
  Answer: (a) Active region
  Explanation: In the active region, the transistor acts as an amplifier with the collector current controlled by the base current.

60. Which of the following devices is bidirectional?

• (a) Diode
• (b) Triac
• (c) MOSFET
• (d) BJT
  Answer: (b) Triac
  Explanation: A Triac can conduct current in both directions and is commonly used in AC power control.

61. What type of feedback is used in an oscillator circuit?

• (a) Positive feedback
• (b) Negative feedback
• (c) No feedback
• (d) Both positive and negative feedback
  Answer: (a) Positive feedback
  Explanation: Positive feedback sustains oscillations by reinforcing the input signal.

62. Which circuit converts DC into AC?

• (a) Rectifier
• (b) Inverter
• (c) Voltage regulator
• (d) Transformer
  Answer: (b) Inverter
  Explanation: Inverters are used to convert direct current (DC) into alternating current (AC).

63. What is the main characteristic of a Schottky diode?

• (a) High forward voltage drop
• (b) Low reverse recovery time
• (c) High breakdown voltage
• (d) High current gain
  Answer: (b) Low reverse recovery time
  Explanation: Schottky diodes are known for their fast switching due to low reverse recovery time.

64. Which transistor configuration offers the highest input impedance?

• (a) Common-emitter
• (b) Common-collector
• (c) Common-base
• (d) Push-pull
  Answer: (b) Common-collector
  Explanation: Common-collector (emitter-follower) configuration provides high input impedance.

65. What is the main function of a flyback diode in inductive loads?

• (a) Regulate current
• (b) Protect against voltage spikes
• (c) Store charge
• (d) Increase the power factor
  Answer: (b) Protect against voltage spikes
  Explanation: A flyback diode prevents high voltage spikes by providing a path for the current when the switch is turned off.

66. In a tuned amplifier, what determines the resonant frequency?

• (a) The amplifier gain
• (b) The power supply voltage
• (c) The LC circuit parameters
• (d) The input impedance
  Answer: (c) The LC circuit parameters
  Explanation: The resonant frequency is determined by the inductance and capacitance values in the LC circuit.

67. Which component provides electrical isolation between input and output?

• (a) Resistor
• (b) Capacitor
• (c) Transformer
• (d) Inductor
  Answer: (c) Transformer
  Explanation: A transformer isolates the input and output while transferring energy.

68. Which filter is used to eliminate 50 Hz hum in power supplies?

• (a) Low-pass filter
• (b) High-pass filter
• (c) Band-pass filter
• (d) Notch filter
  Answer: (d) Notch filter
  Explanation: A notch filter is used to attenuate a specific frequency, such as 50 Hz in power lines.

69. What is the purpose of a heat sink in power amplifiers?

• (a) Increase gain
• (b) Reduce distortion
• (c) Dissipate heat
• (d) Improve input impedance
  Answer: (c) Dissipate heat
  Explanation: Heat sinks help in dissipating excess heat generated by power amplifiers.

70. In a differential amplifier, what happens when both inputs are identical?

• (a) Maximum output
• (b) Zero output
• (c) Amplified output
• (d) Variable output
  Answer: (b) Zero output
  Explanation: When both inputs are equal, the differential input is zero, resulting in no output.

71. What happens when the emitter junction of a BJT is forward biased and the collector junction is reverse biased?

• (a) The transistor is in cut-off
• (b) The transistor is in saturation
• (c) The transistor is in the active region
• (d) The transistor breaks down
  Answer: (c) The transistor is in the active region
  Explanation: In the active region, the BJT amplifies the input signal.

72. What is the purpose of a clamping circuit?

• (a) Limit the amplitude of the input signal
• (b) Shift the DC level of the signal
• (c) Rectify the signal
• (d) Increase the signal frequency
  Answer: (b) Shift the DC level of the signal
  Explanation: Clamping circuits shift the entire signal to a different DC level without changing the shape.

73. Which parameter defines the switching speed of a MOSFET?

• (a) Input impedance
• (b) Gate capacitance
• (c) Threshold voltage
• (d) Saturation current
  Answer: (b) Gate capacitance
  Explanation: The gate capacitance influences how fast the MOSFET can switch between on and off states.

74. Which component is used to block DC while allowing AC to pass?

• (a) Inductor
• (b) Resistor
• (c) Capacitor
• (d) Diode
  Answer: (c) Capacitor
  Explanation: Capacitors block DC components and allow AC signals to pass through.

75. In a Wien bridge oscillator, which component determines the frequency of oscillation?

• (a) Inductor
• (b) Transformer
• (c) RC network
• (d) Zener diode
  Answer: (c) RC network
  Explanation: The frequency of oscillation in a Wien bridge oscillator depends on the values of the resistors and capacitors.

76. Which amplifier is commonly used as a buffer due to its unity gain?

• (a) Inverting amplifier
• (b) Differential amplifier
• (c) Non-inverting amplifier
• (d) Voltage follower
  Answer: (d) Voltage follower
  Explanation: A voltage follower provides high input impedance and unity gain, making it ideal as a buffer.

77. What is the typical voltage drop across a forward-biased silicon diode?

• (a) 0.3 V
• (b) 0.7 V
• (c) 1.1 V
• (d) 2 V
  Answer: (b) 0.7 V
  Explanation: Silicon diodes typically have a forward voltage drop of around 0.7 V.

78. Which of the following is an active component?

• (a) Resistor
• (b) Inductor
• (c) Op-amp
• (d) Capacitor
  Answer: (c) Op-amp
  Explanation: An op-amp is an active component because it requires an external power source to operate.

79. What is the phase difference between the input and output of a common-emitter amplifier?

• (a) 0°
• (b) 90°
• (c) 180°
• (d) 270°
  Answer: (c) 180°
  Explanation: The output of a common-emitter amplifier is inverted, resulting in a 180° phase shift.

80. Which parameter of a transistor is defined as the ratio of collector current to base current?

• (a) Beta (β\betaβ)
• (b) Alpha (α\alphaα)
• (c) Gamma (γ\gammaγ)
• (d) Delta (δ\deltaδ)
  Answer: (a) Beta (β\betaβ)
  Explanation: β\betaβ is the current gain of a transistor in the common-emitter configuration.

81. Which type of filter blocks low frequencies and passes high frequencies?

• (a) Low-pass filter
• (b) High-pass filter
• (c) Band-pass filter
• (d) Notch filter
  Answer: (b) High-pass filter
  Explanation: A high-pass filter allows high-frequency signals to pass while attenuating low-frequency signals.

82. In a differential amplifier, the term “CMRR” stands for:

• (a) Common-mode rejection ratio
• (b) Current modulation response ratio
• (c) Capacitive modulation response ratio
• (d) Collector modulation rejection ratio
  Answer: (a) Common-mode rejection ratio
  Explanation: CMRR measures the ability of a differential amplifier to reject common-mode signals.