Question 1

The total phase shift around a positive feedback loop is
A) 360° or 0°).
B) 180°.
C) 90°.
D) 45°.

Accepted Answer

For a system to oscillate, the total phase shift around a positive feedback loop must be 360° or 0°, which is equivalent, ensuring that the signal reinforces itself each cycle.

Question 2

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

Accepted Answer

Avf = Av / (1 + αvAv) = 244 / (1 + 0.114*244) = 8.47

Question 3

The total phase shift around a negative feedback loop is
A) 360° or 0°).
B) 180°.
C) 90°.
D) 45°.

Accepted Answer

The answer of The total phase shift around a negative...

Question 4

Negative feedback the bandwidth of a noninverting amplifier.
A) increases
B) decreases
C) does not affect
Chapter 15 Operational Amplifiers Answer Key

Accepted Answer

Negative feedback in a noninverting amplifier increases the bandwidth. This is because negative feedback tends to stabilize the amplifier, reducing its gain at low frequencies but extending its usable frequency range, thus increasing the bandwidth.

Question 5

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

Accepted Answer

Negative feedback in electronic circuits typically decreases circuit gain by trading off gain for improvements in other characteristics, such as bandwidth, linearity, and stability.

Question 6

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.

Accepted Answer

Positive feedback is used in the design of oscillators, where the output signal is fed back to the input in phase, thereby reinforcing the signal and sustaining the oscillation.

Question 7

Negative feedback the output impedance of a noninverting amplifier.
A) increases
B) decreases
C) does not affect

Accepted Answer

Negative feedback in a noninverting amplifier configuration decreases the output impedance, making the amplifier better at driving loads.

Question 8

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.

Accepted Answer

The noninverting amplifier typically has a higher Common-Mode Rejection Ratio (CMRR) because the common-mode gain in a noninverting configuration is generally lower than in an inverting configuration, while the differential gain remains high, leading to a higher CMRR value.

Question 9

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

Accepted Answer

An output of 0 V in an inverting amplifier could be caused by either an open input resistor (Ri), which would prevent any signal from reaching the inverting input of the op-amp, or a shorted feedback resistor (Rf), which would effectively ground the output signal, making it 0 V. Both conditions would disrupt the normal operation of the amplifier, leading to a zero output voltage.

Question 10

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

Accepted Answer

The attenuation factor of the circuit is calculated by dividing the feedback voltage (Vf) by the output voltage (Vout). So, the attenuation factor = Vf / Vout = 630 mVpp / 6 Vpp = 0.105.

Question 11

Negative feedback the input impedance of a noninverting amplifier.
A) increases
B) decreases
C) does not affect

Accepted Answer

Negative feedback in a noninverting amplifier increases the input impedance. This is because the feedback tends to stabilize the amplifier's performance, making the input appear as a high impedance to the source.

Question 12

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

Accepted Answer

The voltage follower, being a configuration of an operational amplifier, typically has a high Common Mode Rejection Ratio (CMRR), much greater than 1, indicating its ability to reject common-mode signals and amplify the differential signal.

Quiz 15: Operational Amplifiers

The total phase shift around a positive feedback loop is

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

The total phase shift around a negative feedback loop is

Negative feedback the bandwidth of a noninverting amplifier.

Negative feedback

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

Negative feedback the output impedance of a noninverting amplifier.

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?

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

Negative feedback the input impedance of a noninverting amplifier.

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