Electronic Devices 4-Frequency Response & Amplifiers Flashcards
1
Q
Doubling the voltage gain causes a ________ dB ________.
10, increase
6, increase
10, decrease
6, decrease
A
6, increase
2
Q
________ frequencies are values of frequency at which the RC circuits reduce the voltage gain to 70.7% of its midrange value.
Critical
Cutoff
Corner
all of the above
A
all of the above
3
Q
A roll-off of 20 dB per decade is equivalent to a roll-off of ________ per octave.
3 dB
13 dB
12 dB
6 dB
A
6 dB
4
Q
Each RC circuit causes the gain to drop at a rate of ________ dB/decade.
20
10
6
none of the above
A
20
5
Q
The phase shift through the input of an RC circuit approaches ________° as the frequency approaches zero.
0
45
180
90
A
90
6
Q
Internal transistor junction capacitances affect the high-frequency response of amplifiers by
reducing the amplifier’s gain.
introducing phase shift as the signal frequency increases.
having no effect.
reducing the amplifier’s gain and introducing phase shift as the signal frequency increases.
A
reducing the amplifier’s gain and introducing phase shift as the signal frequency increases.
7
Q
What is the method that can be used to determine the values of fcl and fcu of an amplifier?
five time constants
step-response
sinusoidal
A
step-response
8
Q
The lower critical frequency is also known as the
break frequency.
cutoff frequency.
corner frequency.
all of the above
A
all of the above
9
Q
It is often convenient in amplifiers to assign a certain value of gain as the ________ dB reference.
0
1
6
10
20
A
0
10
Q
For low-frequency response, all RC circuits in an amplifier may not have the same critical frequency. Which RC response will determine the critical frequency of the amplifier?
the lowest frequency
the center frequency
the highest frequency
the bypass frequency
A
the highest frequency
11
Q
A ten-times change in frequency is called a(n)
octave.
decade.
decimal.
none of the above
A
decade.
12
Q
The frequency response of an amplifier can be determined using the step response method, and measuring the output rise/fall times between
0% and 100% response.
10% and 90% response.
25% and 75% response.
five time constant responses.
A
10% and 90% response.
13
Q
In a multistage amplifier, the overall frequency response is determined by the
frequency response of each stage depending on the relationships of the critical frequencies.
frequency response of the first amplifier.
frequency response of the last amplifier.
lower critical frequency of the first amplifier and the upper critical frequency of the final amplifier.
A
frequency response of each stage depending on the relationships of the critical frequencies.
14
Q
What term means that the midrange voltage gain is assigned a value of 1 (or 0 dB)?
critical
Miller
normalized
corner
A
normalized
15
Q
Halving the power corresponds to a ________ dB ________.
3, decrease
10, decrease
3, increase
10, increase
A
3, decrease
16
Q
A two-times change in frequency is called a(n)
binave.
octave.
decade.
none of the above
A
octave
17
Q
A change in frequency by a factor of ________ is equivalent to 1 octave.
2
10
5
20
A
2
18
Q
What is the ratio of the capacitive reactance XCS to the input resistance RI of the input RC circuit of a single-stage BJT amplifier at the low-frequency cutoff?
0.25
0.50
0.75
1.0
A
1.0
19
Q
For which of the following frequency region(s) can the coupling and bypass capacitors no longer be replaced by the short-circuit approximation?
Low-frequency
Mid-frequency
High-frequency
All of the above
A
Low-frequency
20
Q
The smaller capacitive elements of the design will determine the ________ cutoff frequencies.
low
mid
high
A
high
21
Q
What is the range of the capacitor Cds?
0.01 to 0.1 pF
0.1 to 1 pF
0.1 to 1 nF
0.1 to 1 F
A
0.1 to 1 pF
22
Q
The larger capacitive elements of the design will determine the ________ cutoff frequency.
low
mid
high
A
low
23
Q
Which of the following elements is (are) important in determining the gain of the system in the high-frequency region?
Interelectrode capacitances
Wiring capacitances
Miller effect capacitance
All of the above
A
All of the above
24
Q
For audio systems, the reference level is generally accepted as ________.
1 mW
1 W
10 mW
100 mW
A
1mW
25
For the low-frequency response of a BJT amplifier, the maximum gain is where ________ .
RB = 0
RC = 0
RE = 0
RE= 0
26
In the input RC circuit of a single-stage BJT, by how much does the base voltage lead the input voltage at the cutoff frequency in the low-frequency region?
About 0º
45º
About 90º
None of the above
45
27
What is the normalized gain expressed in dB for the cutoff frequencies?
–3 dB
+3 dB
–6 dB
–20 dB
-3 dB
28
Which of the low-frequency cutoffs determined by CS, CC, or CE will be the predominant factor in determining the low-frequency response for the complete system?
lowest
middle
highest
None of the above
highest
29
What is the ratio of the common logarithm of a number to its natural logarithm?
0.435
2
2.3
3.2
2.3
30
Which of the following configurations does (do) not involve the Miller effect capacitance?
Common-emitter
Common-base
Common-collector
All of the above
Common- base
31
By what other name(s) are the cutoff frequencies in a frequency response plot called?
Corner frequency
Break frequency
Half-power frequency
All of the above
All of the above
32
The ________-frequency response of a transformer-coupled system is calculated primarily by the stray capacitance between the turns of the primary and secondary windings.
low
mid
high
high
33
What is the ratio of the output voltage to the input voltage at the cutoff frequencies in a normalized frequency response plot?
0.25
0.50
0.707
1
0.707
34
Which of the following statements is true for a square-wave signal?
It is composed of both even and odd harmonics.
It is composed only of odd harmonics.
It is composed only of even harmonics.
The harmonics waveforms are also square waves.
It is composed only of odd harmonics.
35
A change in frequency by a factor of ________ is equivalent to 1 decade.
2
10
5
20
10
36
Which of the following capacitors is (are) included in Ci for the high-frequency region of a BJT or FET amplifier?
Input wiring capacitance Cw1
The transition capacitance (Cbe/Cqs)
Miller capacitance (Cm1)
All of the above
All of the above
37
In the input RC circuit of a single-stage BJT, by how much does the base voltage lead the input voltage for frequencies much larger than the cutoff frequency in the low-frequency region?
About 0º
45º
About 90º
None of the above
About 0º
38
In the ________-frequency region, the capacitive elements of importance are the interelectrode (between terminals) capacitances internal to the active device and the wiring capacitance between the leads of the network.
low
mid
high
high
39
What is the ratio of the output power to the input power at the cutoff frequencies in a normalized frequency response plot?
0.25
0.50
0.707
1
0.50
40
In which of the following are operational amplifiers (op-amps) used?
Oscillators
Filters
Instrumentation circuits
All of the above
All of the above
41
What is the level of the voltage between the input terminals of an op-amp?
Virtually zero
5 V
18 V
22 V
Virtually zero
42
What is the difference output voltage of any signals applied to the input terminals?
The differential gain times the difference input voltage.
The common-mode gain times the common input voltage.
The sum of the differential gain times the difference input voltage and the common-mode gain times the common input voltage.
The difference of the differential gain times the difference input voltage and the common-mode gain times the common input voltage.
The sum of the differential gain times the difference input voltage and the common-mode gain times the common input voltage.
43
A three-stage op-amp can have a maximum phase lag of ________°.
–180
–90
–270
none of the above
-270
44
What is the open-loop gain of an op-amp at the gain-bandwidth product of the op-amp?
200,000
50,000
200
1
1
45
The ________ amplifier configuration has the highest input impedance and the lowest output impedance of the three basic op-amp configurations.
non-inverting
inverting
voltage-follower
voltage followe
46
An IC unit made using both ________ and ________ transistors is called a ________ circuit.
bipolar, MOSFET, BiFET
bipolar, MOSFET, BiMOS
TTL, MOSFET, TailFET
bipolar, MOSFET, BiMOS
47
The maximum rate of change of the output voltage in response to a step input voltage is the ________ of an op-amp.
time constant
maximum frequency
slew rate
static discharge
slew rate
48
A practical op-amp has very ________ input impedance, very ________ output impedance, very ________ open-loop voltage gain, and a ________ bandwidth.
high, low, high, wide
high, high, low, narrow
low, high, high, wide
low, low, low, wide
high, low, high, wide
49
What is the level of the roll-off in most op-amps?
–6 dB / decade
–20 dB / octave
–6 dB / decade or –20 dB / octave
–20 dB / decade or –6 dB / octave
–20 dB / decade or –6 dB / octave
50
The input offset voltage drift is a parameter directly related to VOS and ________.
ID
power dissipation
temperature
phase shift
temperature
51
What is the difference voltage if the inputs are an ideal opposite signal?
The differential gain times twice the input signal.
The differential gain times the input signal.
The common-mode gain times twice the input signal.
The common-mode gain times the input signal.
The differential gain times twice the input signal.
52
Which of the following circuit conditions affect(s) the output offset voltage of an op-amp?
An input offset voltage, VIO
An input offset current, IIO
Both an input offset voltage, VIO and an input offset current, IIO
None of the above
Both an input offset voltage, VIO and an input offset current, IIO
53
A(n) ________ amplifier configuration has a higher input impedance and a lower output impedance than the op-amp itself.
non-inverting
inverting
voltage-follower
non-inverting
54
n which of the following operations is the resulting output signal of the differential amplifier near zero?
Single-ended
Double-ended
Common-mode
None of the above
Common-mode
55
What is the voltage gain of the unity follower?
0
1
–1
Infinity
1
56
Negative feedback added to an op-amp ________ the bandwidth and ________ the gain.
increases, increases
increases, decreases
decreases, decreases
decreases, increases
increases, decreases
57
What is the scale multiplier (factor) of a basic integrator?
R / C
C / R
–RC
–1 / RC
–1 / RC
58
Which of the following circuits is referred to as a BiMOS circuit?
Bipolar and FET
Bipolar and MOSFET
Opposite-type MOSFETs
None of the above
Bipolar and MOSFET
59
In the differential amplifier circuit, which of the following terminals are connected together?
Bases
Collectors
One base to another collector
Emitters
Emitters
60
The ________ is the voltage gain of an op-amp with external feedback.
Aol
Acl
Av
Acl
61
A(n) ________ amplifier configuration has an input impedance approximately equal to the input resistor Ri and an output impedance approximately equal to the output impedance of the op-amp itself.
inverting
62
What is the difference voltage if the inputs are an ideal in-phase signal?
The differential gain times twice the input signal.
The differential gain times the input signal.
The common-mode gain times twice the input signal.
The common-mode gain times the input signal.
The common-mode gain times the input signal.
63
Open-loop voltage gain of an op-amp can range up to ________.
10,000
50,000
100,000
200,000
200,000
64
Which of the following is (are) the result of gain reduction by a feedback?
The amplifier voltage gain is a more stable and precise value.
The input impedance of the circuit is increased over that of the op-amp alone.
The output impedance is reduced over that of the op-amp alone.
All of the above
All of the above
65
A Schmitt trigger is
a comparator with only one trigger point.
a comparator with hysteresis.
a comparator with three trigger points.
none of the above.
a comparator with hysteresis.
66
The output of a Schmitt trigger is a
pulse waveform.
sawtooth waveform.
sinusoidal waveform.
triangle waveform.
pulse waveform.
67
A comparator with a Schmitt trigger has
two trigger levels.
a fast response.
a slow response.
one trigger level.
two trigger levels.
68
In a(n) ________, when the input voltage exceeds a specified reference voltage, the output changes state.
integrator
differentiator
summing amplifier
comparator
comparator
69
In a flash A/D converter, the priority encoder is used to
select the first input.
select the highest value input.
select the lowest value input.
select the last input.
select the highest value input.
70
What circuit produces an output that approximates the area under the curve of an input function?
integrator
differentiator
summing amplifier
comparator
integrator
71
A good example of hysteresis is a(n)
AM radio.
thermostat.
alarm clock.
none of the above
thermostat
72
To reduce the effects of noise resulting in erratic switching of output states of a comparator, you can use
the upper trigger point.
the lower trigger point.
nonzero-level detection.
hysteresis.
hysteresis
73
What is (are) the necessary component(s) for the design of a bounded comparator?
rectifier diodes
zener diodes
both of the above
zener diodes
74
What type(s) of circuit(s) use comparators?
summer
nonzero-level detector
averaging amplifier
summer and nonzero-level detector
nonzero-level detector
75
A differentiator is used to measure
the sum of the input voltages.
the difference between two voltages.
the area under a curve.
the rate of change of the input voltage.
the rate of change of the input voltage.
76
A(n) ________ amplifier is a summing amplifier with a closed-loop gain equal to the reciprocal of the number of inputs.
averaging
scaling
none of the above
averaging
77
_______ is a mathematical process for determining the rate of change of a function.
Integration
Differentiation
Summing
Comparatoring
Differentiation
78
An integrator circuit
uses a resistor in its feedback circuit.
uses an inductor in its feedback circuit.
uses a capacitor in its feedback circuit.
uses a resistor in its feedback circuit or uses a capacitor in its feedback circuit
uses a capacitor in its feedback circuit.
79
In a comparator with output bounding, what type of diode is used in the feedback loop?
Schottky
junction
zener
varactor
zener
80
A comparator with hysteresis is sometimes known as a(n)
integrator.
differentiator.
Schmitt trigger.
none of the above
Schmitt trigger.
81
Which of the following are variations of the basic summing amplifier?
averaging amplifier
scaling amplifier
both of the above
both of the above
82
The voltage gain of a basic instrumentation amplifier is set by a(n)
diode.
capacitor.
resistor.
inductor.
resistor.
83
A basic ________ amplifier is formed by three op-amps and seven resistors.
instrumentation
isolation
log
antilog
instrumentation
84
Instrumentation amplifiers are normally used to measure
small differential signal voltages.
signals superimposed on a common-mode voltage often much larger than the signal voltage.
both of the above
none of the above
both of the above
85
A(n) ________ amplifier is a differential voltage-gain device that amplifies the difference between the voltages existing at its two input terminals.
instrumentation
isolation
operational transconductance
log
instrumentation
86
The main purpose of an instrumentation amplifier is to amplify ________ signals that are riding on ________ common-mode voltages.
small, small
small, large
large, small
large, large
small, large
87
A log amplifier may use the ________ junction of a BJT in the feedback loop.
base-collector
base-emitter
emitter-collector
emitter-ground
base-emitter
88
A current-to-voltage converter produces a
constant output voltage for a variable input current.
variable output voltage for a constant input current.
proportional output voltage for a variable input current.
proportional output current for a variable input voltage.
proportional output voltage for a variable input current.
89
A log amplifier has ________ in the feedback loop.
a diode
a BJT
a resistor
either a diode or a BJT
either a diode or a BJT
90
What is (are) the principal area(s) of application for isolation amplifiers?
medical
power plant
automation
all of the above
all of the above
91
A constant-current source delivers a load current that
remains constant when the load resistance changes.
varies with load resistance.
varies inversely with load resistance.
varies inversely with input voltage.
remains constant when the load resistance changes.
92
The operational transconductance amplifier (OTA) is primarily a ________ -to- ________ amplifier.
voltage, current
93
The main difference between the isolation amplifier and an instrumentation amplifier is
an instrumentation amplifier has an input stage.
an instrumentation amplifier has an output stage.
an instrumentation amplifier has a differential stage.
the input, output, and power supply stages of an isolation amplifier are all electrically isolated from each other.
the input, output, and power supply stages of an isolation amplifier are all electrically isolated from each other.
94
An antilog amplifier has a ________ in series with the input.
BJT
diode
diode or BJT
resistor
diode or BJT
95
A(n) ________ amplifier provides "a barrier" between the input and output for the protection of human life or sensitive equipment.
instrumentation
isolation
operational transconductance
voltage-to-current
isolation
96
The process known as signal compression is used with a(n) ____ amplifier.
log
antilog
instrumentation
isolation
log
97
Transconductance is the ratio of the output
current to the input voltage.
current to the input current.
voltage to the input voltage.
voltage to the input current.
current to the input voltage.
98
The OTA has a ________ input impedance and a ________ CMRR.
high, low
low, high
high, high
low, low
high, high
99
The log of a number is the
base to which the power must be raised to get that number.
power to which the base must be raised to get that number.
base of that number.
power of that number.
power to which the base must be raised to get that number.
100
What is a key characteristic of an instrumentation amplifier?
high CMRR
high output offset
high output impedance
none of the above
high CMRR
101
In logarithmic signal compression,
large and small voltages are compressed equally.
large voltages are compressed more than small voltages.
large voltages are compressed less than smaller voltages.
none of the above
large voltages are compressed more than small voltages.
102
What part of the characteristic curve of a diode is useful for log amplifiers?
the log region above 0.7 V
the log region below 0.7 V
the log region between 0 V and 0.7 V
the log region below the zener voltage
the log region between 0 V and 0.7 V
103
An OTA has
a bias-current input terminal.
high output impedance.
no fixed open-loop voltage gain.
all of the above
all of the above
104
The main features of a large-signal amplifier is the circuit's ________.
power efficiency
maximum power limitations
impedance matching to the output device
All of the above
All of the above
105
The principal advantage(s) of BJTs over MOSFETs is (are) that
voltage drop across the transistor is important.
they are not as prone to ESD.
both of the above
none of the above
both of the above
106
What is the ratio of the secondary voltage to the primary voltage with the turn ratio in the windings?
N2/N1
(N1/N2)2
(N1/N2)1/3
N1 × N2
N2/N1
107
Class ________ amplifiers are normally operated in a push-pull configuration in order to produce an output that is a replica of the input.
A
B
C
AB
AB
108
Which type of power amplifier is biased for operation at less than 180º of the cycle?
Class A
Class B or AB
Class C
Class D
Class C
109
Class AB operation is ________ operation.
similar to class A
similar to class B
similar to class C
None of the above
None of the above
110
The principal advantage(s) of MOSFETs over BJTs is (are)
their biasing networks are simpler.
their drive requirements are simpler.
they can be connected in parallel for added drive capability.
all of the above
all of the above
111
Which of the following instruments allows more precise measurement of the harmonic components of a distorted signal?
Digital multimeter
Spectrum analyzer
Oscilloscope
Wave analyzer
Wave analyzer
112
In class B operation, at what fraction of VCC should the level of VL(p) be to achieve the maximum power dissipated by the output transistor?
0.5
0.636
0.707
1
0.636
113
What is the maximum temperature rating for silicon power transistors?
50º to 80º
100º to 110º
150º to 200º
250º to 300º
150º to 200º
114
What is the maximum efficiency of a class A circuit with a direct or series-fed load connection?
90%
78.5%
50%
25%
25%
115
Which class of amplifier operates in the linear region for only a small part of the input cycle?
A
B
C
AB
C
116
The Q-point is at cutoff for class ________ operation.
A
B
C
AB
B
117
How many transistors must be used in a class B power amplifier to obtain the output for the full cycle of the signal?
0
1
2
3
2
118
Which of the following is (are) power amplifiers?
Class A
Class B or AB
Class C or D
All of the above
All of the above
119
Quiescent power is the power dissipation of a transistor
with no signal input.
with no load.
under full load.
along the dc load line.
with no signal input.
120
Which of the power amplifiers is not intended primarily for large-signal or power amplification?
Class A
Class B or AB
Class C
Class D
Class C
121
By how much does the output signal vary for a class AB power amplifier?
360º
180º
Between 180º and 360º
Less than 180º
Between 180º and 360º
122
Which type of amplifier uses pulse (digital) signals in its operation?
Class A
Class B or AB
Class C
Class D
Class D
123
Which of the push-pull amplifiers is presently the most popular form of the class B power amplifier?
Quasi-complementary
Transformer-coupled
Complementary-symmetry
None of the above
Quasi-complementary
124
Which amplifier is commonly used as a frequency multiplier?
class A
class B
class C
all of the above
class C
125
A class B amplifier operates in the linear region for
slightly more than 180° of the input cycle.
360° of the input cycle.
slightly less than 180° of the input cycle.
much less than 180° of the input cycle.
slightly less than 180° of the input cycle.
126
Which of the following instruments displays the harmonics of a distorted signal?
Digital multimeter
Spectrum analyzer
Oscilloscope
Wave analyzer
Spectrum analyzer
127
________ amplifiers primarily provide sufficient power to an output load to drive a speaker from a few watts to tens of watts.
Small-signal
Power
None of the above
Power
128
You have an application for a power amplifier to operate on FM radio frequencies. The most likely choice would be a ________ amplifier.
class A
class B
class C
class AB
class C
129
Which of the following describe(s) a power amplifier?
It can handle large power.
It can handle large current.
It does not provide much voltage gain.
All of the above
All of the above
130
Categorize the power efficiency of each class of amplifier, from worst to best.
A, B, AB, D
A, AB, D, B
A, AB, B, D
A, AB, B, D
131
Which operation class is generally used in radio or communications?
A
B
AB
C
D
D
132
In a class AB amplifier, if the VBE drops are not matched to the diode drops or if the diodes are not in thermal equilibrium with the transistors, this can result in
a current mirror.
diode separation.
crossover distortion.
thermal runaway.
thermal runaway.
133
The least efficient amplifier among all classes is
class B.
class A.
class AB.
class C.
class A.
134
In practice, the efficiency of a capacitively coupled class A amplifier is about ________%.
25
40
70
10
10
135
For BJT power transistors, the collector terminal is always connected to the transistor's case
for easy circuit connection.
to prevent shorts.
because the collector terminal is the critical terminal for heat dissipation.
because the collector terminal is located nearest the case.
because the collector terminal is the critical terminal for heat dissipation.
136
Which of the following transistors has been quite popular as the driver device for class D amplification?
BJT
FET
UJT
MOSFET
MOSFET
137
Which of the following is (are) the disadvantage(s) of a class B complementary-symmetry circuit?
It needs two separate voltage sources.
There is crossover distortion in the output signal.
It does not provide exact switching of one transistor off and the other on at the zero-voltage condition.
All of the above
All of the above
138
Which of the power amplifiers has the lowest overall efficiency?
Class A
Class B or AB
Class C
Class D
Class A
139
The maximum efficiency of a class B amplifier is ________ percent.
50
25
70
79
79
140
The maximum efficiency of a transformer-coupled class A amplifier is ________.
25%
50%
78.5%
63.6%
50
141
A class ________ amplifier is biased slightly above cutoff and operates in the linear region for slightly more than 180º of the input cycle.
A
B
C
AB
AB
142
The class ________ amplifier is biased below cutoff.
A
AB
B
C
D
143
What is the maximum efficiency of a class B circuit?
90%
78.5%
50%
25%
78.5
