Deck 15: Operational Amplifiers

Question 1

The circuit in Figure has an output that is approximately

A) 10 Vpp.
B) 11 Vpp.
C) 1 Vpp.
D) Cannot be determined without knowing the value of AOL.

Answer 1

11 Vpp.

Question 2

An op-amp has the part number TL741CN. The prefix TL identifies

A) the operating temperature range.
B) the type of op-amp.
C) the device manufacturer.
D) the type of component casing used.

Answer 2

the device manufacturer.

Question 3

An op-amp has a 3 kΩ load and ±10 V supply voltages. What is the maximum possible peak-to peak output voltage for the circuit?

A) Approximately 18 V
B) Approximately 16 V
C) Approximately 20 V
D) None of the above.

Answer 3

Approximately 16 V

Question 4

Solid-state devices that contain more than one active and/or passive component are called

A) discrete devices.
B) integrated circuits.
C) multiple-component circuits.
D) op-amps.

Question 5

The op-amp in Figure has an output impedance of 100 Ω. The output impedance of the circuit is slightly less than

A) 100 Ω.
B) 100 kΩ.
C) 100.1 kΩ.
D) 50 Ω.

Question 6

An op-amp has a slew rate of 0.2 V/μs. If the the circuit has a sine wave input and its peak output is 15 V, what is its maximum operating frequency?

A) 2.12 kHz
B) 21.2 Hz
C) 471 Hz
D) 4.71 kHz

Question 7

When a given op-amp has 10 V common-mode inputs, the output of the device is 10 mV. When this same device has a 2 mV differential input, the output of the device is 10 V. What is the CMRR of the device?

A) 5:1
B) 5000:1
C) 1000:1
D) 5,000,000:1

Question 8

The op-amp in Figure has an input impedance of 5 MΩ. What is the input impedance of the circuit?

A) 5 MΩ
B) 10 kΩ
C) 50 MΩ
D) 110 kΩ

Question 9

The inverting and noninverting inputs to an op-amp are connected to an)

A) inverting amplifier.
B) noninverting amplifier.
C) differential amplifier.
D) open-loop amplifier.

Question 10

An op-amp will not work if

A) the supply voltages are less than ±5 V.
B) the input offset voltage is less than 100 mV.
C) either the inverting or noninverting input is not provided with an external current path.
D) the input offset current is less than 1 mA.

Question 11

The voltage gain of an op-amp circuit is always less than or equal to the AOL rating for the op-amp.

Question 12

Which of the following statements is true?

A) Op-amps are high-gain dc amplifiers.
B) Op-amps have extremely high input impedance.
C) Op-amps have extremely low output impedance.
D) All of these statements are true.

Question 13

The common-mode gain of the op-amp in Figure is 0.002. What is the CMRR of the amplifier?

A) 25,000:1
B) 0.002:1
C) 100:1
D) Cannot be determined from the information given.

Question 14

The op-amp in Figure has a slew rate of 12 V/μs. If the the circuit has a sine wave input and its peak output is 9 V, what is its maximum operating frequency?

A) approximately 212.2 kHz.
B) approximately 347.2 kHz.
C) approximately 382.0 kHz.
D) None of the above.

Question 15

Why is the CMRR of an inverting amplifier always lower than that of its op-amp?

A) The common-mode gain of an op-amp increases when it is used in an inverting amplifier.
B) The value of differential gain for an inverting amplifier is lower than that of its op-amp.
C) Slew-rate limiting decreases the common-mode gain of the op-amp.
D) Because of the lower input impedance of the inverting amplifier.

Question 16

The value of ACL for the circuit in Figure is

A) 50 k.
B) 200.
C) 50.
D) 51.

Question 17

An op-amp circuit has ±15 V supply voltages and a voltage gain of 20. The noninverting voltage V2) is 0.3 V and the inverting voltage V1) is 0.35 V. What is the output voltage from the device?

A) +1 V
B) +6 V
C) -1 V
D) -7 V

Question 18

A voltage follower has values of RL = 12 kΩ, VS = ±12 V, and Vin = 10 Vpk.What is the peak-to-peak output from the circuit?

A) 20 Vpp
B) 21 Vpp
C) 12 Vpp
D) Cannot be determined from the information given.

Question 19

Op-amps are available in

A) dual in-line packages DIPs).
B) surface-mount packages SMPs)
C) type TO-5 metal cans.
D) all of these packages.

Question 20

The feedback resistor Rf) in Figure opens. What is the peak-to-peak output from the circuit?

A) 11 Vpp clipped)
B) 20 Vpp clipped)
C) 18 Vpp clipped)
D) 18 Vpp not clipped)

Question 21

The total phase shift around a positive feedback loop is

A) 360° or 0°).
B) 180°.
C) 90°.
D) 45°.

Question 22

A negative feedback amplifier has values of αv = 0.114 and Av = 244. What is the value of Avf for the circuit?

A) 8.47
B) 2140
C) 35.1
D) 6.75

Question 23

The total phase shift around a negative feedback loop is

A) 360° or 0°).
B) 180°.
C) 90°.
D) 45°.

Question 24

Negative feedback the bandwidth of a noninverting amplifier.

A) increases
B) decreases
C) does not affect
Chapter 15 Operational Amplifiers Answer Key

Question 25

Negative feedback

A) decreases bandwidth.
B) increases circuit gain.
C) increases amplifier noise.
D) decreases circuit gain.

Question 26

Positive feedback is used to produce a special type of circuit called a/an

A) inverting amplifier.
B) noninverting amplifier.
C) oscillator.
D) feedback regulator.

Question 27

Negative feedback the output impedance of a noninverting amplifier.

A) increases
B) decreases
C) does not affect

Question 28

An inverting amplifier and a noninverting amplifier are built using the same values of Rf and Rin. Assuming that the op-amps being used in the two circuits have identical common-mode gain values, which circuit will have the higher CMRR?

A) The inverting amplifier
B) The noninverting amplifier
C) Neither. The two CMRR values will be equal.

Question 29

An inverting amplifier with ±11 V supply voltages normally has a 10Vpp sinusoidal output. Checking the circuit with an oscilloscope shows that the output is 0 V. Which of the following could account for this problem?

A) Ri open
B) Rf open
C) Rf shorted by a solder bridge
D) either R1 is open or Rf is shorted

Question 30

A negative feedback amplifier has values of Vout = 6 Vpp and Vf = 630 mVpp. What is the attenuation factor of the circuit?

A) 4.28
B) 0.0641
C) 0.105
D) 9.52

Question 31

Negative feedback the input impedance of a noninverting amplifier.

A) increases
B) decreases
C) does not affect

Question 32

The voltage follower typically has a value of CMRR = 1.