Deck 35: Operational Amplifiers

Question 1

An op amp that uses JFETs in the input differential amp and BJTs for the following stages is called a ______________ op amp.

Answer 1

bi-FET

Question 2

The dc current through the emitter resistor is often called the ______________ current.

Answer 2

tail

Question 3

The signal applied to each differential amplifier input is assumed to have exactly the same phase and amplitude, hence the name ______________-mode input.

Answer 3

common

Question 4

It is most common to specify the CMRR in ______________.

Question 5

A(n) ______________ amplifier is a high-gain, direct coupled, differential amplifier.

Question 6

An op amp referred to as the ______________ has become an industry standard.

Question 7

The triangular schematic symbol of an op amp shows only the ______________ connections to different points inside the op amp.

Question 8

The ______________ capacitor of the 741 op amp is used to prevent undesirable oscillations within the op amp.

Question 9

There are two ways to avoid ______________-rate distortion of a sine wave: either use an op amp with a faster slew rate or accept an output waveform with a lower peak voltage.

Question 10

The ______________ input of an op amp has extremely high input impedance, but its value is not the input impedance of the circuit.

Question 11

An op amp specification indicating the maximum rate at which the output voltage can change is referred to as the

A) zero crossing rate
B) change rate
C) slew rate
D) input offset rate

Question 12

Slew-rate distortion of a sine wave produces what type waveform?

A) cosine wave
B) square wave
C) rectangular wave
D) triangular wave

Question 13

The highest undistorted frequency out of an op amp without slew-rate distortion is called the

A) power bandwidth (f_max)
B) resonant frequency (f_r)
C) fundamental frequency
D) harmonic frequency

Question 14

Two identical signals applied to the inputs of an op amp, each with exactly the same phase relationship and voltage values is called a(n)

A) common-mode signal
B) differential input
C) balanced-mode signal
D) identical-mode signal

Question 15

What is the sampling of a portion of the output signal from an amplifier and feeding it back either to aid or oppose the input signal called?

A) sample rate
B) open loop
C) feedback
D) regulation

Question 16

Which of the following is not an advantage of negative feedback?

A) stabilize voltage gain
B) improve input and output impedances
C) increase amplifier selectivity
D) increase amplifier bandwidth

Question 17

When the voltage at the op amp's inverting input is at the same potential as ground, but it can sink no current, this point is considered

A) chassis ground
B) ground loop
C) virtual ground
D) grounded

Question 18

What determines how much of the op amp's output signal is fed back to the input?

A) virtual ground
B) feedback fraction
C) power source
D) input signal

Question 19

What determines the voltage gain of a noninverting op amp?

A) input signal
B) virtual ground
C) power source
D) R_F and R_i

Question 20

Which of the following is not another name for op amp voltage follower?

A) unity gain amplifier
B) instrumentation amplifier
C) buffer amplifier
D) isolation amplifier

Question 21

Because the stages inside of an op amp are direct coupled,

A) there is no lower cutoff frequency
B) there is no upper cutoff frequency
C) there is no need for a power source
D) the lower cutoff frequency is 100 Hz

Question 22

The frequency at which the closed-loop gain decreases to 70.7% of its maximum is called the

A) resonant frequency
B) harmonic frequency
C) closed-loop cutoff frequency
D) open-loop cutoff frequency

Question 23

If an op amp's closed-loop voltage gain is decreased

A) the bandwidth will decrease
B) the bandwidth will increase
C) the closed-loop cutoff frequency will be lower
D) the open-loop cutoff frequency will be lower

Question 24

With an inverting op amp, the input and output signals are

A) in phase
B) 90° out of phase
C) 180° out of phase
D) 45° out of phase

Question 25

An amplifier whose output voltage equals the negative sum of the input voltages is called a(n)

A) difference amplifier
B) adding amplifier
C) summing amplifier
D) negative sum amplifier

Question 26

When each input voltage of a summing amplifier is amplified by a different factor, the circuit is called a

A) factor amplifier
B) sum / difference amplifier
C) scaling amplifier
D) voltage amplifier

Question 27

Circuits that can amplify differential input signals but reject or attenuate common-mode input signals is called a(n)

A) attenuation amplifier
B) common-mode amplifier
C) differential amplifier
D) subtracting amplifier

Question 28

With the instrumentation amplifier shown in Figure 33-19, A₁ and A₂ are in what op amp configuration?

A) inverting
B) noninverting
C) voltage follower
D) differential

Question 29

The differential amplifier shown in Figure has a gain equal to

A) -R_F/R1
B) R_F/R1
C) R_F/R2
D) R_F/R3

Question 30

A filter that uses components or devices such as transistors and op amps, which can amplify, is called a(n)

A) active filter
B) passive filter
C) notch filter
D) wavetrap

Question 31

The output of a comparator is always

A) inverted
B) noninverted
C) ±V_sat
D) a common-mode signal

Question 32

Because the comparator's output voltage switches when V_in crosses zero, the circuit is sometimes called a

A) zero-crossing detector
B) zero detector
C) zero-switching detector
D) zero comparator

Question 33

What can be used with diodes to rectify signals with peak values in the millivolt region?

A) bipolar junction transistors
B) MOSFETs
C) JFETs
D) op amps

Question 34

The first stage of every operational amplifier is a

A) differential amplifier
B) noninverting amplifier
C) comparator
D) voltage follower

Question 35

Operational amplifiers are linear ICs that can be used to amplify signal frequencies that extend from 0 Hz to well above 1 MHz.

Question 36

The first stage of every op amp is an emitter follower.

Question 37

An op amp that uses JFETs in the input differential amp and bipolar transistors for the following stages is called a bi-FET op amp.

Question 38

A differential amp has one input called the inverting input, one input called the noninverting input, and one output.

Question 39

The signal applied to the input of a differential amplifier is assumed to have exactly the same phase and amplitude and is referred to as the common-mode input.

Question 40

The common-mode rejection ratio is usually defined as the ratio of the differential voltage gain to the common-mode voltage gain.

Question 41

The lower the value of CMRR, the better the differential amplifier.

Question 42

An op amp is a high-gain, direct coupled, differential amplifier.

Question 43

The 741 op amp, an industry standard is contained in an eight-pin IC and is made by several manufacturers.

Question 44

Bi-FET op amps generally have a wider bandwidth, higher slew rate, larger power output, higher input impedances, and much lower input bias currents.

Question 45

Designed into the 741 op amp is a compensating capacitor used to prevent undesirable oscillations within the op amp.

Question 46

The open-loop voltage gain of an op amp is its voltage gain when there is negative feedback.

Question 47

The open-loop voltage gain of an op amp is the ratio of its output voltage to its differential input voltage.

Question 48

Input offset current is the difference between the op amp's two input bias currents.

Question 49

Open-loop cutoff frequency is the frequency at which the open-loop voltage gain of an op amp is down to 70.7% of its maximum value at dc.