# Operational Amplifiers (Op-amp) MCQ Posted by

## Operational Amplifiers (Op-amp) MCQ

Operational Amplifiers (Op-amp) MCQ, Op-amp MCQ, Multiple Choice Questions on Op-amp, Objective Questions on Operational Amplifiers (Op-amp), Operational Amplifiers (Op-amp) questions with answers, GATE questions on Operational Amplifiers (Op-amp), Engineering MCQ, Electronics Device MCQ

### Multiple Choice Questions

Q.1. A differential amplifier ………..

• is a part of an OP-amp
• has one input and one output
• both
• none of the above

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

• the output is grounded
• one input is grounded and signal is applied to the other
• both inputs are connected together
• the output is not inverted

Answer: one input is grounded and signal is applied to the other

Q.3. In differential-mode, …………..

• opposite polarity signals are applied to the inputs
• the gain is one
• the outputs are of different amplitudes
• only one supply voltage is used

Answer: opposite polarity signals are applied to the inputs

Q.4. In the common-mode, …………..

• both inputs are grounded
• the outputs are connected together
• an identical signal appears on both inputs
• the output signals are in-phase

Answer: an identical signal appears on both inputs

Q.5. The common-mode gain is ….

• very high
• very low
• always unity
• unpredictable

Q.6. The differential gain is ….

• very high
• very low
• dependent on input voltage

Q.7. If ADM = 3500 and ACM = 0.35, the CMRR is ….

• 1225
• 10,000
• 80 dB
• 10,000 & 80 dB

Q.8. With zero volts on both inputs, an OP-amp ideally should have an output ….

• equal to the positive supply voltage
• equal to the negative supply voltage
• equal to zero
• equal to the CMRR

Q.9. Of the values listed, the most realistic value for open-loop voltage gain of an OP-amp is ….

• 1
• 2000
• 80 dB
• 100,000

Q.10. A certain OP-amp has bias currents of 50 μA and 49.3 μA. The input offset current is ….

• 700 nA
• 99.3 μA
• 49.7 μA
• none of these

Q. 11. The output of a particular OP-amp increases 8 V in 12 μs. The slew rate is ….

• 90 V/μs
• 0.67 V/μs
• 1.5 V/μs
• none of these

Q.12. For an OP-amp with negative feedback, the output is ….

• equal to the input
• increased
• feed back to the inverting input
• feed back to the noninverting input

Answer: feed back to the inverting input

Q.13. The use of negative feedback ….

• reduces the voltage gain of an OP-amp
• makes linear operation possible
• both
• none of the above

Q.14. Negative feedback ….

• increases the input and output impedances
• increases the input impedance and bandwidth
• decreases the output impedance and bandwidth
• does not affect impedance or bandwidth

Answer: increases the input impedance and bandwidth

Q.15. A certain noninverting amplifier has Ri of 1 kΩ and Rf of 100 kΩ. The closed-loop voltage gain is ….

• 100,000
• 1000
• 101
• 100

Q.16. If feedback resistor in Q.15 is open, the voltage gain ……………

• increases
• decreases
• is not affected
• depends on Ri

Q.17. 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 ……….

• doubles
• drops to 12.5
• remains at 25
• increases slightly

Q.18. A voltage follower ….

• has a voltage gain of 1
• in noninverting
• has no feedback resistor
• has all of these

Q.19. The OP-amp can amplify ….

• a.c. signals only
• d.c. signals only
• both a.c. and d.c. signals
• neither d.c. nor a.c. signals

Answer: both a.c. and d.c. signals

Q.20. The input offset current equals the ….

• difference between two base currents
• average of two base currents
• collector current divided by current gain
• none of these

Answer: difference between two base currents

Q.21. The tail current of a differential amplifier is ….

• half of either collector current
• equal to either collector current
• two times either collector current
• equal to the difference in base currents

Answer: two times either collector current

Q.22. The node voltage at the top of the tail resistor is closest to ….

• collector supply voltage
• zero
• emitter supply voltage
• tail current times base resistance

Q.23. The tail current in a differential amplifier equals ….

• difference between two emitter currents
• sum of two emitter currents
• collector current divided by current gain
• collector voltage divided by collector resistance

Answer: sum of two emitter currents

Q.24. The differential voltage gain of a differential amplifier is equal to RC divided by ….

• r′e
• r′e/2
• 2 r′e
• RE

Q.25. The input impedance of a differential amplifier equals r′e times ….

• β
• RE
• RC

Q.26. A common-mode signal is applied to ….

• the noninverting input
• the inverting input
• both inputs
• top of the tail resistor

Q.27. The common-mode voltage gain is ….

• smaller than differential voltage gain
• equal to differential voltage gain
• greater than differential voltage gain
• none of the above

Answer: smaller than differential voltage gain

Q.28. The input stage of an OP-amp is usually a ….

• differential amplifier
• class B push-pull amplifier
• CE amplifier
• swamped amplifier

Q,29. The common-mode voltage gain of a differential amplifier is equal to RC divided by ….

• r′e
• 2 r′e
• r′e /2
• 2 RE