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Unit 5: Operational Amplifiers and Applications - Practice Quiz

ECE226 — Analog Electronic Devices And Circuits 60 Questions
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1 What does the abbreviation "Op-Amp" stand for?

Introduction to Op-Amp Easy
A. Open-loop Amplifier
B. Operating Amplitude
C. Operational Amplifier
D. Optical Amplifier

2 An operational amplifier is basically a:

Introduction to Op-Amp Easy
A. Low-gain single-ended amplifier
B. Power amplifier only
C. Tuned RF amplifier
D. High-gain differential amplifier

3 The IC 741 op-amp is typically available in an 8-pin package. How many pins does this standard package have?

Block Diagram and Pin Configuration of 741 Op-Amp Easy
A. 8
B. 4
C. 14
D. 16

4 In the internal block diagram of an op-amp, which stage is directly connected to the two input terminals?

Block Diagram and Pin Configuration of 741 Op-Amp Easy
A. Output driver stage
B. Intermediate gain stage
C. Differential amplifier stage
D. Level shifter stage

5 In the 741 op-amp, the offset null pins are used to:

Block Diagram and Pin Configuration of 741 Op-Amp Easy
A. Set the supply voltage
B. Increase the open-loop gain
C. Cancel the output offset voltage
D. Adjust the slew rate

6 What is the open-loop voltage gain of an ideal op-amp?

Characteristics of Ideal Op-Amp Easy
A. Infinite
B. One hundred
C. Zero
D. Unity

7 The input impedance of an ideal op-amp is:

Characteristics of Ideal Op-Amp Easy
A. Equal to the load resistance
B. Infinite
C. Zero
D. Around 50

8 What is the output impedance of an ideal op-amp?

Characteristics of Ideal Op-Amp Easy
A. Zero
B. Infinite
C. Equal to input impedance
D. Very high

9 For an ideal op-amp, the bandwidth is considered to be:

Characteristics of Ideal Op-Amp Easy
A. Equal to the slew rate
B. Infinite
C. Limited to 1 kHz
D. Zero

10 CMRR in an op-amp stands for:

CMRR Easy
A. Current Mode Rejection Ratio
B. Combined Mode Response Ratio
C. Common Mode Resistance Ratio
D. Common Mode Rejection Ratio

11 For a good op-amp, the value of CMRR should be:

CMRR Easy
A. As high as possible
B. Exactly zero
C. Exactly equal to unity
D. As low as possible

12 The slew rate of an op-amp is usually expressed in units of:

Slew Rate Easy
A.
B.
C.
D.

13 Slew rate is defined as the maximum rate of change of which quantity?

Slew Rate Easy
A. Output voltage
B. Feedback resistance
C. Supply voltage
D. Input current

14 A differential amplifier amplifies the:

Differential Amplifier Configurations Easy
A. Sum of two input signals
B. Product of two input signals
C. Difference between two input signals
D. Ratio of two input signals

15 For an inverting amplifier with input resistor and feedback resistor , the closed-loop gain is:

Op-Amp Applications Inverting and Non-Inverting amplifiers Easy
A.
B.
C.
D.

16 The closed-loop voltage gain of a non-inverting amplifier is given by:

Op-Amp Applications Inverting and Non-Inverting amplifiers Easy
A.
B.
C.
D.

17 In an inverting amplifier, the inverting input terminal is said to be at:

Concept of Virtual Ground Easy
A. Virtual ground
B. Positive supply voltage
C. Twice the input voltage
D. Negative supply voltage

18 A summing amplifier is used to:

Summing and Difference Amplifiers Easy
A. Divide input voltages
B. Multiply two voltages
C. Add several input voltages together
D. Subtract one voltage from another

19 What is the voltage gain of an op-amp voltage follower?

Voltage Follower Easy
A. Ten
B. Zero
C. Unity (1)
D. Infinite

20 In an op-amp integrator, which component is placed in the feedback path?

Differentiator and Integrator Easy
A. Diode
B. Capacitor
C. Inductor
D. Resistor

21 An inverting amplifier uses and . If the input voltage is , what is the output voltage?

Op-Amp Applications Inverting and Non-Inverting amplifiers Medium
A.
B.
C.
D.

22 A non-inverting amplifier has and . What is its closed-loop voltage gain?

Op-Amp Applications Inverting and Non-Inverting amplifiers Medium
A.
B.
C.
D.

23 An op-amp has a differential gain of and a common-mode gain of . What is its CMRR in dB?

CMRR Medium
A.
B.
C.
D.

24 An op-amp has a slew rate of . What is the maximum frequency at which it can produce an undistorted sine wave output of peak?

Slew Rate Medium
A.
B.
C.
D.

25 In an ideal inverting amplifier, why is the inverting input terminal called a virtual ground?

Concept of Virtual Ground Medium
A. Because it is held at approximately by feedback while no current flows into the op-amp input
B. Because it is physically connected directly to the ground terminal of the power supply
C. Because the output voltage at that node is always exactly zero regardless of input
D. Because the non-inverting terminal supplies a large current to keep it grounded

26 Which set of parameters correctly describes an ideal op-amp?

Characteristics of Ideal Op-Amp Medium
A. Zero open-loop gain, infinite input impedance, infinite output impedance
B. Infinite open-loop gain, zero input impedance, zero output impedance
C. Finite open-loop gain, zero input impedance, infinite output impedance
D. Infinite open-loop gain, infinite input impedance, zero output impedance

27 In a summing amplifier with and three input resistors each , inputs are , and . What is the output?

Summing and Difference Amplifiers Medium
A.
B.
C.
D.

28 What is the primary purpose of using a voltage follower (unity-gain buffer) in a circuit?

Voltage Follower Medium
A. Amplifying a small signal by a large voltage gain factor
B. Inverting the phase of the input signal by
C. Converting an AC signal into a DC voltage level
D. Impedance matching by providing high input impedance and low output impedance

29 For an ideal op-amp integrator with input resistor and feedback capacitor , the output voltage is proportional to:

Differentiator and Integrator Medium
A. The logarithm of the input voltage
B. The integral of the input voltage
C. The square of the input voltage
D. The derivative of the input voltage

30 In an op-amp differentiator with and , if the input rises linearly at , what is the output voltage?

Differentiator and Integrator Medium
A.
B.
C.
D.

31 In the standard 8-pin DIP package of the 741 op-amp, which pins are used for offset null adjustment?

Block Diagram and Pin Configuration of 741 Op-Amp Medium
A. Pins 6 and 8
B. Pins 1 and 5
C. Pins 2 and 3
D. Pins 4 and 7

32 When an op-amp is used as a comparator with the reference at the inverting input, what happens when (at non-inverting input) exceeds the reference?

Comparators Medium
A. Output oscillates continuously
B. Output saturates to positive supply rail
C. Output remains at
D. Output saturates to negative supply rail

33 A difference amplifier has all four resistors equal (). If (non-inverting side) and (inverting side), what is the output?

Summing and Difference Amplifiers Medium
A.
B.
C.
D.

34 An op-amp is fundamentally a:

Introduction to Op-Amp Medium
A. High-gain direct-coupled differential amplifier
B. Fixed-gain current amplifier with capacitive coupling
C. Low-gain power amplifier with transformer coupling
D. Single-ended AC-coupled voltage amplifier

35 Which differential amplifier configuration provides the highest common-mode rejection?

Differential Amplifier Configurations Medium
A. Constant-current source (current-mirror) biased emitter
B. Single-ended input with grounded second input
C. Simple resistor-biased emitter with low resistance
D. Open-collector configuration without emitter resistor

36 In a datasheet, the parameter 'Input Offset Voltage' () refers to:

understanding datasheets of op-amps Medium
A. The difference between the two supply rail voltages
B. The output voltage present when both inputs are grounded and no correction applied
C. The differential input voltage needed to make the output zero
D. The maximum voltage the input pins can tolerate safely

37 An inverting amplifier is required to have a gain of . If , what value of is needed?

Op-Amp Applications Inverting and Non-Inverting amplifiers Medium
A.
B.
C.
D.

38 Slew rate limiting in an op-amp primarily causes which type of distortion for large-amplitude high-frequency sine waves?

Slew Rate Medium
A. The output DC offset drifts to the positive rail
B. The output phase leads the input by
C. The output becomes triangular rather than sinusoidal
D. The output amplitude doubles unexpectedly

39 In a voltage follower, how is the feedback arranged?

Voltage Follower Medium
A. Output connected directly to the inverting input (100% negative feedback)
B. Output connected to both inputs through equal resistors
C. Output connected through a large resistor to the non-inverting input
D. Output left open with feedback taken from the supply

40 The concept of a 'virtual short' between the two input terminals of an op-amp with negative feedback is valid because:

Characteristics of Ideal Op-Amp Medium
A. Infinite open-loop gain forces the differential input voltage toward zero
B. The two input terminals are physically wired together internally
C. The output impedance is infinite, isolating the inputs from the load
D. The input impedance is zero so both terminals share the same current

41 An op-amp has a slew rate of . For an output sine wave of peak amplitude , what is the maximum frequency (full-power bandwidth) before slew-rate distortion occurs?

Slew Rate Hard
A.
B.
C.
D.

42 A differential amplifier has a differential gain of and a common-mode gain of . If both inputs receive a common-mode signal of plus a differential signal of , what is the ratio of the wanted output to the unwanted output?

CMRR Hard
A.
B.
C.
D.

43 An op-amp datasheet lists and open-loop differential gain . What is the approximate common-mode gain ?

CMRR Hard
A.
B.
C.
D.

44 In an inverting amplifier with and , why does the summing junction remain at approximately despite carrying signal current?

Concept of Virtual Ground Hard
A. The input resistor drops the entire input voltage to zero regardless of feedback
B. Negative feedback forces the inverting input to track the grounded non-inverting input due to near-infinite open-loop gain
C. The op-amp output actively drives the node to ground potential using its internal reference
D. The feedback resistor shorts the node directly to ground through a low impedance path

45 An ideal integrator has and . A step input of is applied at . What is the output voltage at (assuming initially discharged capacitor)?

Differentiator and Integrator Hard
A.
B.
C.
D.

46 Why is a resistor often added in series with the input capacitor of a practical differentiator?

Differentiator and Integrator Hard
A. To limit high-frequency gain and improve stability against high-frequency noise
B. To increase the differentiation constant at all frequencies uniformly
C. To provide a DC path that eliminates the differentiating action entirely
D. To convert the differentiator into an integrator above the corner frequency

47 A summing amplifier has inputs , , through resistors , , and respectively, with . What is the output voltage?

Summing and Difference Amplifiers Hard
A.
B.
C.
D.

48 A non-inverting amplifier is designed for a gain of . If the op-amp has a finite open-loop gain of , what is the actual closed-loop gain (accounting for gain error)?

Op-Amp Applications Inverting and Non-Inverting amplifiers Hard
A.
B.
C.
D.

49 A Schmitt trigger (inverting) uses saturation and feedback resistors (to non-inverting input) and (to output). What is the total hysteresis width (difference between upper and lower thresholds)?

Comparators Hard
A.
B.
C.
D.

50 Which combination of parameters correctly describes an ideal op-amp?

Characteristics of Ideal Op-Amp Hard
A. Infinite input impedance, zero output impedance, infinite gain, infinite bandwidth
B. Zero input impedance, infinite output impedance, infinite gain, zero bandwidth
C. Infinite input impedance, infinite output impedance, finite gain, infinite bandwidth
D. Zero input impedance, zero output impedance, infinite gain, finite bandwidth

51 Two op-amps A and B have identical unity-gain bandwidths but A has twice the slew rate of B. For a small-amplitude, high-frequency sine wave well within both bandwidths, which statement is true?

Slew Rate Hard
A. Op-amp B distorts because lower slew rate limits all frequencies
B. Op-amp A always produces a cleaner output regardless of amplitude
C. Neither can reproduce the signal because slew rate governs small-signal response
D. Both reproduce the signal similarly since slew rate limiting does not dominate for small signals

52 In the 741 op-amp's internal block diagram, which stage is primarily responsible for providing high voltage gain?

Block Diagram and Pin Configuration of 741 Op-Amp Hard
A. The intermediate common-emitter stage with an active current-source load
B. The input differential amplifier stage
C. The level-shifting and biasing network
D. The output push-pull class-AB stage

53 A voltage follower is used to buffer a sensor with source resistance driving a load. What is the primary benefit compared to direct connection?

Voltage Follower Hard
A. It provides voltage gain while inverting the polarity of the signal
B. It increases the source resistance seen by the load to reduce current
C. It amplifies the sensor signal by the ratio of load to source resistance
D. It prevents loading of the sensor, delivering nearly the full source voltage to the load

54 In a BJT differential amplifier, replacing the emitter resistor with a constant-current source improves which parameter most significantly?

Differential Amplifier Configurations Hard
A. Differential gain, by lowering the emitter degeneration
B. Input offset voltage, by matching the transistors better
C. Slew rate, by increasing the tail current abruptly
D. CMRR, by increasing the effective common-mode emitter impedance

55 A difference amplifier uses and . If a common-mode signal appears at both inputs but is mistakenly , what happens?

Summing and Difference Amplifiers Hard
A. The differential gain drops to zero while common-mode gain becomes maximum
B. A small common-mode error appears at the output due to resistor mismatch
C. The common-mode signal is amplified by the full differential gain of
D. The output remains exactly zero because ideal op-amps reject common-mode

56 A datasheet specifies input bias current and input offset current . In an inverting amplifier with , what compensation resistor value at the non-inverting input minimizes output error due to bias current, given ?

understanding datasheets of op-amps Hard
A.
B.
C.
D.

57 Why does an op-amp require negative feedback for most linear applications despite having very high open-loop gain?

Introduction to Op-Amp Hard
A. To increase the open-loop gain further beyond its intrinsic value
B. To set a precise, stable closed-loop gain that is largely independent of the variable open-loop gain
C. To convert the op-amp into a comparator with defined thresholds
D. To eliminate the need for a dual power supply in operation

58 An inverting amplifier has and . What is its input resistance seen by the source, and its gain?

Op-Amp Applications Inverting and Non-Inverting amplifiers Hard
A. Input resistance , gain
B. Input resistance , gain
C. Input resistance , gain
D. Input resistance , gain

59 What is the key advantage of a comparator with hysteresis (Schmitt trigger) over a simple comparator when processing a slowly varying noisy input?

Comparators Hard
A. It increases output switching speed by boosting the slew rate
B. It amplifies the noise so the true signal becomes clearer at the output
C. It provides a linear output proportional to the input near the threshold
D. It prevents multiple false transitions by requiring the input to cross separated thresholds

60 Applying the two 'golden rules' (virtual short and no input current) to a non-inverting amplifier with (to ground) and (feedback), what is the closed-loop gain?

Characteristics of Ideal Op-Amp Hard
A.
B.
C.
D.
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