Operational Amplifiers MCQ Questions & Answers

Operational Amplifiers MCQs : This section focuses on the "Operational Amplifiers". These Multiple Choice Questions (MCQs) should be practiced to improve the Operational Amplifiers skills required for various interviews (campus interview, walk-in interview, company interview), placement, entrance exam and other competitive examinations.

Question 1

An output that is proportional to the addition of two or more inputs is from which type of amplifier?

A. differentiator

B. difference

C. summing

D. analog subtractor

Question 2

Op-amps used as high- and low-pass filter circuits employ which configuration?

A. noninverting

B. comparator

C. open-loop

D. inverting

Question 3

With negative feedback, the returning signal:

A. aids the input signal

B. is proportional to output current

C. opposes the input signal

D. is proportional to differential voltage gain

Question 4

Which of these is incorrect for an operational amplifier?

A. It has a high voltage gain

B. It is a direct coupled amplifier

C. It is only useful for amplifying AC signals

D. It was originally designed to perform mathematical operations

Question 5

In an ideal op-amp, which is not true?

A. Open loop voltage gain is infinite

B. Input resistance is infinite

C. Slew rate is infinite

D. CMRR is zero

Question 6

The voltage follower has a:

A. closed-loop voltage gain of unity

B. small open-loop voltage gain

C. closed-loop bandwidth of zero

D. large closed-loop output impedance

Question 7

The unity gain bandwidth for an op-amp having open loop gain 2×106 is 10 Mhz. Calculate the AC gain of op-amp at an input of 2000 Hz.

A. 2000

B. 5000

C. 10000

D. 12.5

Question 8

The closed-loop voltage gain of an inverting amplifier equals:

A. the ratio of the input resistance to the feedback resistance

B. the open-loop voltage gain

C. the feedback resistance divided by the input resistance

D. the input resistance

Question 9

What three subcircuits does a phase locked loop (PLL) consist of?

A. phase comparator, comparator, and VCO

B. phase comparator, bandpass filter, and VCO

C. phase comparator, bandpass filter, and demodulator

D. phase comparator, low-pass filter, and VCO

Question 10

An ideal operational amplifier has

A. infinite output impedance

B. zero input impedance

C. infinite bandwidth

D. All of the above

Question 11

Consider a Miller integrator with a time constant of 1ms and an input resistance of 10 kΩ. Let the op amp have VOS (offset voltage) = 2 mV and output saturation voltages of ±12 V. Select the largest possible value for a feedback resistor RF so that at least ±10 V of output signal swing remains available.

A. 10 kΩ

B. 100 kΩ

C. 1 MΩ

D. 10 MΩ

Question 12

A series dissipative regulator is an example of a:

A. linear regulator

B. switching regulator

C. shunt regulator

D. dc-to-dc converter

Question 13

The ratio between differential gain and common-mode gain is called:

A. amplitude

B. differential-mode rejection

C. common-mode rejection

D. phase

Question 14

If ground is applied to the (+) terminal of an inverting op-amp, the (–) terminal will:

A. not need an input resistor

B. be virtual ground

C. have high reverse current

D. not invert the signal

Question 15

Given that for an op-amp the gain is 103, the slew rate is 1.5V/μsec. Input is 5×10-3sinωt, calculate maximum frequency to prevent distortion.

A. 47.7 kHz

B. 0.3 MHz

C. 477 Hz

D. 3 kHz

Question 16

Till what frequency do we get amplification from IC 741?

A. Unity gain bandwidth

B. 3-dB frequency

C. Infinity

D. UGB + fOL

Question 17

Another name for a unity gain amplifier is:

A. difference amplifier

B. comparator

C. single ended

D. voltage follower

Question 18

The negative feedback causes the input voltage difference to ____________

A. 1

B. Increase

C. Decrease

D. 0

Question 19

A portion of the output that provides circuit stabilization is considered to be:

A. negative feedback

B. distortion

C. open-loop

D. positive feedback

Question 20

Consider an inverting amplifier circuit designed using an op amp and two resistors, R1 = 10 kΩ and R2 = 1 MΩ. If the op amp is specified to have an input bias current of 100 nA and an input offset current of 10 nA, find the output dc offset voltage resulting.

A. 0.1 mV

B. 1 mV

C. 10 mV

D. 100 mV

Question 21

A noninverting closed-loop op-amp circuit generally has a gain factor:

A. less than one

B. greater than one

C. of zero

D. equal to one

Question 22

The number of terminals in an Op-amp ______________

A. 6

B. 2

C. 5

D. 3

Question 23

What is the difference between common-mode and differential-mode input signals?

A. phase relationship

B. voltage

C. current

D. apparent power

Question 24

Consider a Miller integrator with a time constant of 1ms and an input resistance of 10 kΩ. Let the op amp have VOS (offset voltage) = 2 mV and output saturation voltages of ±12 V. What is the corner frequency of the resulting STC network?

A. 1 Hz

B. 0.16 Hz

C. 0.33 Hz

D. 0.5 Hz

Question 25

Consider an inverting amplifier with a nominal gain of 1000 constructed from an op amp with an input offset voltage of 3 mV and with output saturation levels of ±10 V. If the effect of VOs(input offset voltage) is nulled at room temperature (250C). The circuit is to operate at a temperature in the range 0°C to 75°C and the temperature coefficient of VOS is 10 μV/°C?

A. 8.5 mV

B. 9 mV

C. 9.5 mV

D. 10 mV

Question 26

When a capacitor is used in place of a resistor in an op-amp network, its placement determines:

A. open- or closed-loop gain

B. integration or differentiation

C. saturation or cutoff

D. addition or subtraction

Question 27

The Schmitt trigger is a two-state device that is used for:

A. pulse shaping

B. peak detection

C. input noise rejection

D. filtering

Question 28

An astable multivibrator is also known as a:

A. one-shot multivibrator

B. free-running multivibrator

C. bistable multivibrator

D. monostable multivibrator

Question 29

A circuit that uses an amplifier with passive filter elements is called a(n):

A. relaxation oscillator

B. signal generator

C. differential amplifier

D. active filter

Question 30

The common-mode voltage gain is

A. smaller than differential voltage gain

B. equal to voltage gain

C. greater than differential voltage gain

D. None of the above

Question 31

Consider an inverting amplifier with a nominal gain of 1000 constructed from an op amp with an input offset voltage of 3 mV and with output saturation levels of ±10 V. If the effect of VOs(input offset voltage) is nulled at room temperature (250C), how large an input can one now apply if the circuit is to operate at a constant temperature?

A. 8.5 mV

B. 9 mV

C. 9.5 mV

D. 10 mV

Question 32

The input offset current equals the

A. average of two base currents

B. collector current divided by the current gain

C. difference between two base-emitter voltages

D. difference between two base currents

Question 33

If the gain of a closed-loop inverting amplifier is 3.9, with an input resistor value of 1.6 kilohms, what value of feedback resistor is necessary?

A. 6240 ohms

B. 2.4 kilohms

C. 410 ohms

D. 0.62 kilohms

Question 34

What starts a free-running multivibrator?

A. a trigger

B. an input signal

C. an external circuit

D. nothing

Question 35

Consider an inverting amplifier with a nominal gain of 1000 constructed from an op amp with an input offset voltage of 3 mV and with output saturation levels of ±10 V. What is (approximately) the peak sine-wave input signal that can be applied without output clipping?

A. 7 mV

B. 10 mV

C. 13 mV

D. 9mV

Question 36

The magnitude of closed-loop voltage gain (Acl) of an inverting amplifier equals:

A. the ratio of the input resistance to the feedback resistance

B. the open-loop voltage gain Aol

C. the feedback resistance divided by the input resistance

D. the input resistance

Question 37

If the input to a comparator is a sine wave, the output is a:

A. ramp voltage

B. sine wave

C. rectangular wave

D. sawtooth wave

Question 38

If the output voltage is not a linear function of input voltage then ____________

A. Op-amp acts a linear device

B. Op-amp acts as a non-linear device

C. Op-amp acts a polar device

D. Op-amp acts as an inverter

Question 39

An ideal amplifier should have:

A. high input current

B. zero offset

C. high output impedance

D. moderate gain

Question 40

Given that CMRR is 100dB. Input common-mode voltage is 12 V. Differential voltage gain is 4000. Calculate output common-mode voltage.

A. 48V

B. 0.48V

C. 20V

D. 11V

Question 41

In order for an output to swing above and below a zero reference, the op-amp circuit requires:

A. a resistive feedback network

B. zero offset

C. a wide bandwidth

D. a negative and positive supply

Question 42

The open-loop voltage gain (Aol) of an op-amp is the

A. external voltage gain the device is capable of

B. internal voltage gain the device is capable of

C. most controlled parameter

D. same as Acl

Question 43

With negative feedback, the returning signal

A. is proportional to the output current

B. is proportional to the differential voltage gain

C. opposes the input signal

D. aids the input signal

Question 44

How many logic states does an S-R flip-flop have?

A. 2

B. 3

C. 4

D. 5

Question 45

Op-amp was introduced by __________

A. Fairchild

B. Maxwell

C. Rutherford

D. Sahani

Question 46

A practical op-amp has a bandwidth of only 10 Hz. Gain is 106, and the required bandwidth is 100 kHz. How much feedback is required?

A. 0.99% negative feedback

B. 0.99% positive feedback

C. 1% negative feedback

D. 1% positive feedback

Question 47

The major difference between ground and virtual ground is that virtual ground is only a:

A. voltage reference

B. current reference

C. power reference

D. difference reference

Question 48

When the input voltage difference is small in magnitude, the Op-amp behaves as ____________

A. Non-linear device

B. Linear device

C. Complex device

D. Bipolar device

Question 49

In an open-loop op-amp circuit, whenever the inverting input (–) is negative relative to the noninverting input (+), the output will:

A. swing negative

B. close the loop

C. be balanced

D. swing positive

Question 50

The Op-amp is a type of ___________

A. Differential amplifier

B. Integrated amplifier

C. Isolation amplifier

D. Feedback amplifier

Question 51

If the feedback/input resistor ratio of a feedback amplifier is 4.6 with 1.7 V applied to the noninverting input, what is the output voltage value?

A. 7.82 V

B. saturation

C. cutoff

D. 9.52 V

Question 52

In a PLL, to obtain lock, the signal frequency must:

A. come within the lock range

B. be less than the capture frequency

C. come within the capture range

D. be greater than the capture frequency

Question 53

How many leads does the TO-5 metal can package of an operational amplifier have?

A. 8, 10, or 12

B. 6, 8, or 10

C. 8 or 14

D. 8 or 16

Question 54

Consider a Miller integrator with a time constant of 1ms and an input resistance of 10 kΩ. Let the op amp have VOS (offset voltage) = 2 mV and output saturation voltages of ±12 V. Assuming that when the power supply is turned on the capacitor voltage is zero, how long does it take for the amplifier to saturate?

A. 3s

B. 6s

C. 9s

D. 12s

Question 55

If a noninverting amplifier has an RIN of 1000 ohms and an RFB of 2.5 kilohms, what is the RIN voltage when 1.42 mV is applied to the correct input?

A. 3.5 mV

B. ground

C. 1.42 mV

D. 0.56 mV

Question 56

All of the following are basic op-amp input modes of operation EXCEPT

A. inverting mode

B. common-mode

C. double-ended

D. single-ended

Question 57

With a differential gain of 50,000 and a common-mode gain of 2, what is the common-mode rejection ratio?

A. –87.9 dB

B. –43.9 dB

C. 43.9 dB

D. 87.9 dB

Question 58

Input impedance [Zin(I)] of an inverting amplifier is approximately equal to:

A. Ri

B. Rf + Ri

C. ∞

D. Rf – Ri

Question 59

If an op-amp has one input grounded and the other input has a signal feed to it, then it is operating as what?

A. Common-mode

B. Single-ended

C. Double-ended

D. Noninverting mode

Question 60

What is the use of the compensation capacitor in op-amp?

A. Improves the amplification of op-amp

B. Decreases the slew rate of op-amp

C. Increases the bandwidth of op-amp

D. Op-amp acts as all pass filter

Question 61

A circuit whose output is proportional to the difference between the input signals is considered to be which type of amplifier?

A. common-mode

B. darlington

C. differential

D. operational

Question 62

A differential amplifier has a common-mode gain of 0.2 and a common-mode rejection ratio of 3250. What would the output voltage be if the single-ended input voltage was 7 mV rms?

A. 1.4 mV rms

B. 650 mV rms

C. 4.55 V rms

D. 0.455 V rms