# 50 TOP OP-AMP Questions and Answers pdf | MCQs

## OP AMP Questions and Answers pdf :-

1. A differential amplifier ……………..

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

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

Ans : 2

3. 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

Ans : 1

4. In the common mode, ……………

both inputs are grounded
the outputs are connected together
an identical signal appears on both the inputs
the output signal are in-phase
Ans : 3

5. The common-mode gain is ………..

very high
very low
always unity
unpredictable
Ans : 2

6. The differential gain is ………

very high
very low
dependent on input voltage
Ans : 1

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

1225
10,000
80 dB
Ans : 4

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 CMRR
Ans : 3

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
Ans : 4

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

700 nA
99.3 µA
49.7 µA
none of these
Ans : 1

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

90 V/µs
0.67 V/µs
1.5 V/µs
none of these
Ans : 2

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

equal to the input
increased
fed back to the inverting input
fed back to the noninverting input
Ans : 3

13. The use of negative feedback ………

reduces the voltage gain of an Op-amp
makes the Op-amp oscillate
makes linear operation possible
Ans : 4

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
Ans : 2

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

100,000
1000
101
100
Ans : 3

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

increases
decreases
is not affected
depends on Ri
Ans : 1

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
Ans : 3

18. A voltage follower ……….

has a voltage gain of 1
is noninverting
has no feedback resistor
has all of these
Ans : 4

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
Ans : 3

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
Ans : 1

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
Ans : 3

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

collector supply voltage
zero
emitter supply voltage
tail current times base resistance
Ans : 2

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
Ans : 2

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

r’e
r’e/2
2r’e
RE
Ans : 3

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

ß
RE
RC

Ans : 4

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

the noninverting input
the inverting input
both iputs
top of the tail resistor
Ans : 3

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

smaller than differentail voltage gain
equal to differential voltage gain
greater than differential voltage gain
none of the above
Ans : 1

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

differential amplifier
class B push-pull amplifier
CE amplifier
swamped amplifier
Ans : 1

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

r’e
2r’e
r’e/2
2RE
Ans : 4

30. Current cannot flow to ground through …….

a mechanical ground
an a.c. ground
a virtual ground
an ordinary ground
Ans : 3