Deck 17: Negative Feedback

Question 1

Negative feedback reduces harmonic distortion.

Answer 1

True

Question 2

Loop gain is the op amp's voltage gain of the forward and feedback paths.

Answer 2

True

Question 3

Negative feedback can stabilize voltage gain,increase input impedance,and decrease output impedance.

Answer 3

True

Question 4

The current-controlled voltage source amplifier is an almost perfect current-to-voltage converter because it has zero input impedance and zero output impedance.

Question 5

A voltage-controlled current source (VCIS)is also called a voltage-to-current converter.

Question 6

The input to a negative-feedback amplifier can only be a voltage.

Question 7

A current-controlled current source has a

A) very low input impedance and a very high output impedance.
B) very high input impedance and a very low output impedance.
C) very high input impedance and a very high output impedance.
D) very low input impedance and a very low output impedance.

Question 8

The feedback attenuation factor indicates how much of the output voltage is attenuated before the feedback signal reaches the inverting input of an op amp.

Question 9

For a given op amp,the gain-bandwidth product is

A) very low.
B) very high.
C) a variable.
D) a constant.

Question 10

How does negative feedback increase the bandwidth of an amplifier?

A) the roll-off in open-loop voltage gain means less voltage is fed back, which produces more input voltage as compensation
B) the roll-off in open-loop voltage gain means more voltage is fed back, which produces more input voltage as compensation
C) the roll-off in closed-loop voltage gain means less voltage is fed back, which produces less input voltage as compensation
D) the roll-off in closed-loop voltage gain means more voltage is fed back, which produces less input voltage as compensation

Question 11

The closed-loop impedance of a voltage-controlled voltage source is very small,usually much smaller than its input resistance.

Question 12

With a voltage-controlled current source,an input current controls an output current.

Question 13

Nonlinear distortion called harmonic distortion can be measured with an oscilloscope.

Question 14

The conversion factor for the current-controlled voltage source (ICVS)is called transconductance and expressed in siemens (mhos).

Question 15

A current-controlled current source is an ideal current amplifier because it has a stabilized current gain,zero input impedance,and infinite output impedance.

Question 16

What effect does negative feedback have on slew-rate distortion?

A) more feedback less distortion
B) less feedback less distortion
C) more feedback more distortion
D) none

Question 17

The closed-loop output impedance is the overall output impedance looking back into the voltage-controlled voltage source amplifier.

Question 18

The worst-case error of closed-loop voltage gain occurs when the op amp open-loop voltage gain is minimum.

Question 19

A current-controlled voltage source is sometimes called a transresistance amplifier.

Question 20

Because of the heavy negative feedback,the current-controlled current source tends to act like a perfect

A) current-to-voltage converter.
B) voltage-to-current converter.
C) voltage amplifier.
D) current amplifier.

Question 21

The closed-loop input impedance of a voltage-controlled voltage source is usually

A) much larger than R_in but less than R_CM.
B) much less than Rin but larger than RCM.
C) much larger than Rin and RCM.
D) much less than Rin and RCM.

Question 22

The voltage-controlled current source is also called a

A) current-to-voltage converter.
B) transresistance amplifier.
C) voltage-to-current converter.
D) regenerative feedback amplifier.

Question 23

The input to a negative-feedback amplifier is

A) a voltage only.
B) a current only.
C) either voltage or current.
D) regenerative.

Question 24

Types of circuits that use negative feedback does not include

A) voltage-controlled voltage source.
B) current-controlled voltage source.
C) transconductance amplifier.
D) transistor amplifier.

Question 25

The effects of negative feedback does not include

A) stabilize voltage gain.
B) increase input impedance.
C) increase output impedance.
D) decrease output impedance.

Question 26

A transresistance amplifier is another name for the

A) voltage-controlled voltage source.
B) current-controlled voltage source.
C) voltage-controlled current source.
D) current-controlled current source.

Question 27

The voltage-controlled voltage source voltage gain of the forward and feedback paths is called

A) feedback gain.
B) loop gain.
C) negative gain.
D) forward gain.

Question 28

The conversion factor of the voltage-controlled current source is called ________.

A) translucence
B) transconductance
C) transresistance
D) transistorized

Question 29

Coupling capacitors can be added to a voltage-controlled voltage source prototype in order to get

A) higher gain.
B) ower gain.
C) less distortion.
D) an ac amplifier.

Question 30

The overall output impedance looking back into the voltage-controlled voltage source amplifier is called the

A) voltage source output impedance.
B) voltage-controlled output impedance.
C) open-loop output impedance.
D) closed-loop output impedance.

Question 31

What term describes the action of negative feedback that almost eliminates the internal op amp variations and makes the closed-loop voltage gain dependent primarily on external resistances?

A) regulates
B) attenuates
C) stabilizes
D) neutralizes

Question 32

The worst-case error of closed-loop voltage gain occurs when the open-loop voltage gain is ________.

A) greater than 10
B) less than 10
C) maximum
D) minimum

Question 33

Which negative feedback amplifier is considered an almost perfect current-to-voltage converter because it has zero input impedance and zero output impedance?

A) current-controlled voltage source
B) voltage-controlled voltage source
C) transconductance amplifier
D) current-controlled current source

Question 34

Harmonic distortion can be measured with a

A) signature analyzer.
B) frequency generator.
C) frequency counter.
D) distortion analyzer.

Question 35

Nonlinear distortion is often referred to as

A) modulation distortion.
B) transistor noise.
C) harmonic distortion.
D) feedback distortion.

Question 36

Op amps generally have a much higher value of common-mode input resistance than do discrete bipolar diff amps because

A) a current mirror is used.
B) an emitter resistor is used.
C) a compensating capacitor is used.
D) regenerative feedback is used.

Question 37

What is the term that is used to describe how much the output voltage is attenuated before the feedback signal reaches the inverting input?

A) feedback attenuation factor
B) inverting feedback factor
C) output feedback factor
D) input feedback factor

Question 38

What stabilizes the voltage gain and has an enhancing effect on quantities such as gain stability,distortion,offsets,input impedance and output impedance?

A) loop gain
B) positive feedback
C) attenuated feedback
D) harmonics

Question 39

Negative feedback

A) increases harmonic distortion.
B) reduces harmonic distortion.
C) causes harmonic distortion.
D) has no effect on harmonic distortion.

Question 40

A transconductance amplifier is another name for the

A) voltage-controlled voltage source.
B) current-controlled voltage source.
C) voltage-controlled current source.
D) current-controlled current source.

Question 41

What concept is reinforced by noting that all of the input current of the current-controlled voltage source amplifier must flow through the feedback resistor?

A) loop gain
B) feedback fraction B
C) virtual ground
D) gain-bandwidth product

Question 42

For an undistorted output over the entire closed-loop bandwidth,the closed-loop cutoff frequency must be

A) less than the power bandwidth.
B) more than the power bandwidth.
C) equal to the power bandwidth.
D) above 20 kHz.

Question 43

Which negative amplifier has a very small input impedance and a very large output impedance and can be considered an almost perfect current amplifier?

A) voltage-controlled voltage source
B) transresistance amplifier
C) transconductance amplifier
D) current-controlled current source

Question 44

The op amp has an open-loop voltage gain of approximately ________.

A) 100
B) 1000
C) 10,000
D) 100,000

Question 45

Which type of negative feedback amplifier is shown in Figure 17-9?

A) voltage-controlled voltage source
B) transresistance amplifier
C) transconductance amplifier
D) current-controlled current source

Question 46

With a voltage-controlled current source,an input

A) voltage controls an output current.
B) current controls an output voltage.
C) voltage controls an output voltage.
D) current controls an output current.

Question 47

If an op amp does not have enough gain-bandwidth product for an application,a designer can

A) use a different application.
B) add discrete amplifiers.
C) select a better op amp.
D) use discrete amplifiers instead.

Question 48

What is the feedback attenuation factor for the amplifier shown in Figure 17-4?

A) 0.25
B) 0.025
C) 3.9
D) 2.5

Question 49

What type of negative feedback amplifier is shown in Figure 17-4?

A) voltage-controlled voltage source
B) transresistance amplifier
C) transconductance amplifier
D) current-controlled current source