Multiple Choice Questions and Answers on Op-Amp ( Operational Amplifier )

Multiple Choice Questions and Answers on Op-Amp ( Operational Amplifier )

Q1. A differential amplifier ……………..

  1. is a part of an Op-amp
  2. has one input and one output
  3. has two outputs
  4. answers (1) and (2)

Answer : 4

Q 2. When a differential amplifier is operated single-ended, …………

  1. the output is grounded
  2. one input is grounded and signal is applied to the other
  3. both inputs are connected together
  4. the output is not inverted

Answer : 2

Q3. In differential-mode, …………….

  1. opposite polarity signals are applied to the inputs
  2. the gain is one
  3. the outputs are of different amplitudes
  4. only one supply voltage is used

Answer : 1

Q4. In the common mode, ……………

  1. both inputs are grounded
  2. the outputs are connected together
  3. an identical signal appears on both the inputs
  4. the output signal are in-phase

Answer : 3

Q5. The common-mode gain is ………..

  1. very high
  2. very low
  3. always unity
  4. unpredictable

Answer : 2

Q6. The differential gain is ………

  1. very high
  2. very low
  3. dependent on input voltage
  4. about 100

Answer : 1

Q7. If ADM = 3500 and ACM = 0.35, the CMRR is ……….

  1. 1225
  2. 10,000
  3. 80 dB
  4. answers (1) and (3)

Answer : 4

Q8. With zero volts on both inputs, an OP-amp ideally should have an output ………..

  1. equal to the positive supply voltage
  2. equal to the negative supply voltage
  3. equal to zero
  4. equal to CMRR

Answer : 3

Q9. Of the values listed, the most realistic value for open-loop voltage gain of an OP-amp is ……

  1. 1
  2. 2000
  3. 80 dB
  4. 100,000

Answer : 4

Q10. A certain OP-amp has bias currents of 50 μA. The input offset current is ……..

  1. 700 nA
  2. 99.3 μA
  3. 49.7 μA
  4. none of these

Answer : 1

Q11. The output of a particular Op-amp increases 8V in 12μs. The slew rate is …….

  1. 90 V/μs
  2. 0.67 V/μs
  3. 1.5 V/μs
  4. none of these

Answer : 2

Q12. For an Op-amp with negative feedback, the output is …….

  1. equal to the input
  2. increased
  3. fed back to the inverting input
  4. fed back to the noninverting input

Answer : 3

Q13. The use of negative feedback ………

  1. reduces the voltage gain of an Op-amp
  2. makes the Op-amp oscillate
  3. makes linear operation possible
  4. answers (1) and (2)

Answer : 4

Q14. Negative feedback ………..

  1. increases the input and output impedances
  2. increases the input impedance and bandwidth
  3. decreases the output impedance and bandwidth
  4. does not affect impedance or bandwidth

Answer : 2

Q15. A certain noninverting amplifier has Ri of 1 kΩ and Rf of 100 kΩ. The closed-loop voltage gain is ………

  1. 100,000
  2. 1000
  3. 101
  4. 100

Answer : 3

Q16. If the feedback resistor in Q15 (above question) is open, the voltage gain …….

  1. increases
  2. decreases
  3. is not affected
  4. depends on  Ri

Answer : 1

Q17. A certain inverting amplifier has a closed-loop voltage gain of 25. The Op-amp has an open-loop voltage gain of 100,000. If an Op-amp with an open-loop voltage gain of 200,000 is substituted in the arrangement, the closed-loop gain ……..

  1. doubles
  2. drops to 12.5
  3. remains at 25
  4. increases slightly

Answer : 3

Q18. A voltage follower ……….

  1. has a voltage gain of 1
  2. is noninverting
  3. has no feedback resistor
  4. has all of these

Answer : 4

Q19. The Op-amp can amplify

  1. a.c. signals only
  2. d.c. signals only
  3. both a.c. and d.c. signals
  4. neither d.c. nor a.c. signals

Answer : 3

Q20. The input offset current equals the ……….

  1. difference between two base currents
  2. average of two base currents
  3. collector current divided by current gain
  4. none of these

Answer : 1

Q21. The tail current of a differential amplifier is …….

  1. half of either collector current
  2. equal to either collector current
  3. two times either collector current
  4. equal to the difference in base currents

Answer : 3

Q22. The node voltage at the top of the til resistor is closes to ……….

  1. collector supply voltage
  2. zero
  3. emitter supply voltage
  4. tail current times base resistance

Answer : 2

Q23. The tail current in a differential amplifier equals …….

  1. difference between two emitter currents
  2. sum of two emitter currents
  3. collector current divided by current gain
  4. collector voltage divided by collector resistance

Answer : 2

Q24. The differential voltage gain of a differential amplifier is equal to RC divided by …….

  1. r’e
  2. r’e/2
  3. 2r’e
  4. RE

Answer : 3

Q25. The input impedance of a differential amplifier equals r’e times ……

  1. β
  2. RE
  3. RC

Answer : 4

Q26.  A common-mode signal is applied to ……….

  1. the noninverting input
  2. the inverting input
  3. both iputs
  4. top of the tail resistor

Answer : 3

Q27. The common-mode voltage gain is ………

  1. smaller than differentail voltage gain
  2. equal to differential voltage gain
  3. greater than differential voltage gain
  4. none of the above

Answer : 1

Q28. The input stage of an Op-amp is usually a ……….

  1. differential amplifier
  2. class B push-pull amplifier
  3. CE amplifier
  4. swamped amplifier

Answer : 1

Q29. The common-mode voltage gain of a differential amplifier is equal to Rdivided by ……..

  1. r’e
  2. 2r’e
  3. r’e/2
  4. 2RE

Answer : 4

Q30. Current cannot flow to ground through …….

  1. a mechanical ground
  2. an a.c. ground
  3. a virtual ground
  4. an ordinary ground

Answer : 3