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Amateur Radio 2024 - Extra > E7 - PRACTICAL CIRCUITS [8 Exam Questions - 8 Groups] 108 Questions > Flashcards

E7 - PRACTICAL CIRCUITS [8 Exam Questions - 8 Groups] 108 Questions Flashcards

1
Q

“Which circuit is bistable?”

A. An AND gate
B. An OR gate
C. A flip-flop
D. A bipolar amplifier

A

C. A flip-flop

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2
Q

“What is the function of a decade counter?”

A. It produces one output pulse for every 10 input pulses
B. It decodes a decimal number for display on a seven-segment LED display
C. It produces 10 output pulses for every input pulse
D. It decodes a binary number for display on a seven-segment LED display

A

A. It produces one output pulse for every 10 input pulses

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3
Q

“Which of the following can divide the frequency of a pulse train by 2?”

A. An XOR gate
B. A flip-flop
C. An OR gate
D. A multiplexer

A

B. A flip-flop

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4
Q

“How many flip-flops are required to divide a signal frequency by 4?”

A. 1
B. 2
C. 4
D. 8

A

B. 2

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5
Q

“Which of the following is a circuit that continuously alternates between two states without an external clock?”

A. Monostable multivibrator
B. J-K flip-flop
C. T flip-flop
D. Astable multivibrator

A

D. Astable multivibrator

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6
Q

“What is a characteristic of a monostable multivibrator?”

A. It switches momentarily to the opposite binary state and then returns to its original state after a set time
B. It produces a continuous square wave oscillating between 1 and 0
C. It stores one bit of data in either a 0 or 1 state
D. It maintains a constant output voltage, regardless of variations in the input voltage

A

A. It switches momentarily to the opposite binary state and then returns to its original state after a set time

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7
Q

“What logical operation does a NAND gate perform?”

A. It produces logic 0 at its output only when all inputs are logic 0
B. It produces logic 1 at its output only when all inputs are logic 1
C. It produces logic 0 at its output if some but not all inputs are logic 1
D. It produces logic 0 at its output only when all inputs are logic 1

A

D. It produces logic 0 at its output only when all inputs are logic 1

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8
Q

“What logical operation does an OR gate perform?”

A. It produces logic 1 at its output if any or all inputs are logic 1
B. It produces logic 0 at its output if all inputs are logic 1
C. It only produces logic 0 at its output when all inputs are logic 1
D. It produces logic 1 at its output if all inputs are logic 0

A

A. It produces logic 1 at its output if any or all inputs are logic 1

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9
Q

“What logical operation is performed by an exclusive NOR gate?”

A. It produces logic 0 at its output only if all inputs are logic 0
B. It produces logic 1 at its output only if all inputs are logic 1
C. It produces logic 0 at its output if only one input is logic 1
D. It produces logic 1 at its output if only one input is logic 1

A

C. It produces logic 0 at its output if only one input is logic 1

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10
Q

“What is a truth table?”

A. A table of logic symbols that indicate the high logic states of an op-amp
B. A diagram showing logic states when the digital device output is true
C. A list of inputs and corresponding outputs for a digital device
D. A table of logic symbols that indicate the logic states of an op-amp

A

C. A list of inputs and corresponding outputs for a digital device

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11
Q

“What type of logic defines “1” as a high voltage?”

A. Reverse Logic
B. Assertive Logic
C. Negative logic
D. Positive Logic

A

D. Positive Logic

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12
Q

“For what portion of the signal cycle does each active element in a push-pull Class AB amplifier conduct?”

A. More than 180 degrees but less than 360 degrees
B. Exactly 180 degrees
C. The entire cycle
D. Less than 180 degrees

A

A. More than 180 degrees but less than 360 degrees

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13
Q

“What is a Class D amplifier?”

A. A type of amplifier that uses switching technology to achieve high efficiency
B. A low power amplifier that uses a differential amplifier for improved linearity
C. An amplifier that uses drift-mode FETs for high efficiency
D. A frequency doubling amplifier

A

A. A type of amplifier that uses switching technology to achieve high efficiency

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14
Q

“Which of the following components form the output of a class D amplifier circuit?”

A. A low-pass filter to remove switching signal components
B. A high-pass filter to compensate for low gain at low frequencies
C. A matched load resistor to prevent damage by switching transients
D. A temperature compensating load resistor to improve linearity

A

A. A low-pass filter to remove switching signal components

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15
Q

“Where on the load line of a Class A common emitter amplifier would bias normally be set?”

A. Approximately halfway between saturation and cutoff
B. Where the load line intersects the voltage axis
C. At a point where the bias resistor equals the load resistor
D. At a point where the load line intersects the zero bias current curve

A

A. Approximately halfway between saturation and cutoff

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16
Q

“What can be done to prevent unwanted oscillations in an RF power amplifier?”

A. Tune the stage for maximum SWR
B. Tune both the input and output for maximum power
C. Install parasitic suppressors and/or neutralize the stage
D. Use a phase inverter in the output filter

A

C. Install parasitic suppressors and/or neutralize the stage

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17
Q

“Which of the following amplifier types reduces even-order harmonics?”

A. Push-push
B. Push-pull
C. Class C
D. Class AB

A

B. Push-pull

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18
Q

“Which of the following is a likely result when a Class C amplifier is used to amplify a single-sideband phone signal?”

A. Reduced intermodulation products
B. Increased overall intelligibility
C. Signal inversion
D. Signal distortion and excessive bandwidth

A

D. Signal distortion and excessive bandwidth

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19
Q

“How can an RF power amplifier be neutralized?”

A. By increasing the driving power
B. By reducing the driving power
C. By feeding a 180-degree out-of-phase portion of the output back to the input
D. By feeding an in-phase component of the output back to the input

A

C. By feeding a 180-degree out-of-phase portion of the output back to the input

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20
Q

“Which of the following describes how the loading and tuning capacitors are to be adjusted when tuning a vacuum tube RF power amplifier that employs a Pi-network output circuit?”

A. The loading capacitor is set to maximum capacitance and the tuning capacitor is adjusted for minimum allowable plate current
B. The tuning capacitor is set to maximum capacitance and the loading capacitor is adjusted for minimum plate permissible current
C. The loading capacitor is adjusted to minimum plate current while alternately adjusting the tuning capacitor for maximum allowable plate current
D. The tuning capacitor is adjusted for minimum plate current, and the loading capacitor is adjusted for maximum permissible plate current

A

D. The tuning capacitor is adjusted for minimum plate current, and the loading capacitor is adjusted for maximum permissible plate current

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21
Q

“In Figure E7-1, what is the purpose of R1 and R2?”

A. Load resistors
B. Voltage divider bias
C. Self bias
D. Feedback

A

B. Voltage divider bias

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22
Q

“In Figure E7-1, what is the purpose of R3?”

A. Fixed bias
B. Emitter bypass
C. Output load resistor
D. Self bias

A

D. Self bias

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23
Q

“What type of amplifier circuit is shown in Figure E7-1?”

A. Common base
B. Common collector
C. Common emitter
D. Emitter follower

A

C. Common emitter

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24
Q

“Which of the following describes an emitter follower (or common collector) amplifier?”

A. A two-transistor amplifier with the emitters sharing a common bias resistor
B. A differential amplifier with both inputs fed to the emitter of the input transistor
C. An OR circuit with only one emitter used for output
D. An amplifier with a low impedance output that follows the base input voltage

A

D. An amplifier with a low impedance output that follows the base input voltage

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25
Q

“Why are switching amplifiers more efficient than linear amplifiers?”

A. Switching amplifiers operate at higher voltages
B. The power transistor is at saturation or cutoff most of the time
C. Linear amplifiers have high gain resulting in higher harmonic content
D. Switching amplifiers use push-pull circuits

A

B. The power transistor is at saturation or cutoff most of the time

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26
Q

“What is one way to prevent thermal runaway in a bipolar transistor amplifier?”

A. Neutralization
B. Select transistors with high beta
C. Use a resistor in series with the emitter
D. All these choices are correct

A

C. Use a resistor in series with the emitter

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27
Q

“What is the effect of intermodulation products in a linear power amplifier?”

A. Transmission of spurious signals
B. Creation of parasitic oscillations
C. Low efficiency
D. All these choices are correct

A

A. Transmission of spurious signals

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28
Q

“Why are odd-order rather than even-order intermodulation distortion products of concern in linear power amplifiers?”

A. Because they are relatively close in frequency to the desired signal
B. Because they are relatively far in frequency from the desired signal
C. Because they invert the sidebands causing distortion
D. Because they maintain the sidebands, thus causing multiple duplicate signals

A

A. Because they are relatively close in frequency to the desired signal

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29
Q

“What is a characteristic of a grounded-grid amplifier?”

A. High power gain
B. High filament voltage
C. Low input impedance
D. Low bandwidth

A

C. Low input impedance

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30
Q

“How are the capacitors and inductors of a low-pass filter Pi-network arranged between the network’s input and output?”

A. Two inductors are in series between the input and output, and a capacitor is connected between the two inductors and ground
B. Two capacitors are in series between the input and output, and an inductor is connected between the two capacitors and ground
C. An inductor is connected between the input and ground, another inductor is connected between the output and ground, and a capacitor is connected between the input and output
D. A capacitor is connected between the input and ground, another capacitor is connected between the output and ground, and an inductor is connected between input and output

A

D. A capacitor is connected between the input and ground, another capacitor is connected between the output and ground, and an inductor is connected between input and output

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31
Q

“Which of the following is a property of a T-network with series capacitors and a parallel shunt inductor?”

A. It is a low-pass filter
B. It is a band-pass filter
C. It is a high-pass filter
D. It is a notch filter

A

C. It is a high-pass filter

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32
Q

“What advantage does a series-L Pi-L-network have over a series-L Pi-network for impedance matching between the final amplifier of a vacuum-tube transmitter and an antenna?”

A. Greater harmonic suppression
B. Higher efficiency
C. Does not require a capacitor
D. Greater transformation range

A

A. Greater harmonic suppression

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33
Q

“How does an impedance-matching circuit transform a complex impedance to a resistive impedance?”

A. It introduces negative resistance to cancel the resistive part of impedance
B. It introduces transconductance to cancel the reactive part of impedance
C. It cancels the reactive part of the impedance and changes the resistive part to a desired value
D. Reactive currents are dissipated in matched resistances

A

C. It cancels the reactive part of the impedance and changes the resistive part to a desired value

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34
Q

“Which filter type is described as having ripple in the passband and a sharp cutoff?”

A. A Butterworth filter
B. An active LC filter
C. A passive op-amp filter
D. A Chebyshev filter

A

D. A Chebyshev filter

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35
Q

“What are the distinguishing features of an elliptical filter?”

A. Gradual passband rolloff with minimal stop band ripple
B. Extremely flat response over its pass band with gradually rounded stop band corners
C. Extremely sharp cutoff with one or more notches in the stop band
D. Gradual passband rolloff with extreme stop band ripple

A

C. Extremely sharp cutoff with one or more notches in the stop band

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36
Q

“Which describes a Pi-L-network used for matching a vacuum tube final amplifier to a 50-ohm unbalanced output?”

A. A Phase Inverter Load network
B. A Pi-network with an additional series inductor on the output
C. A network with only three discrete parts
D. A matching network in which all components are isolated from ground

A

B. A Pi-network with an additional series inductor on the output

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37
Q

“Which of the following factors has the greatest effect on the bandwidth and response shape of a crystal ladder filter?”

A. The relative frequencies of the individual crystals
B. The DC voltage applied to the quartz crystal
C. The gain of the RF stage preceding the filter
D. The amplitude of the signals passing through the filter

A

A. The relative frequencies of the individual crystals

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38
Q

“What is a crystal lattice filter?”

A. A power supply filter made with interlaced quartz crystals
B. An audio filter made with four quartz crystals that resonate at 1 kHz intervals
C. A filter using lattice-shaped quartz crystals for high-Q performance
D. A filter with narrow bandwidth and steep skirts made using quartz crystals ~~

A

D. A filter with narrow bandwidth and steep skirts made using quartz crystals ~~

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39
Q

“Which of the following filters would be the best choice for use in a 2 meter band repeater duplexer?”

A. A crystal filter
B. A cavity filter
C. A DSP filter
D. An L-C filter

A

B. A cavity filter

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40
Q

“Which of the following describes a receiving filter’s ability to reject signals occupying an adjacent channel?”

A. Passband ripple
B. Phase response
C. Shape factor
D. Noise factor

A

C. Shape factor

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41
Q

“What is one advantage of a Pi-matching network over an L-matching network consisting of a single inductor and a single capacitor?”

A. The Q of Pi-networks can be controlled
B. L-networks cannot perform impedance transformation
C. Pi-networks are more stable
D. Pi-networks provide balanced input and output

A

A. The Q of Pi-networks can be controlled

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42
Q

“How does a linear electronic voltage regulator work?”

A. It has a ramp voltage as its output
B. It eliminates the need for a pass transistor
C. The control element duty cycle is proportional to the line or load conditions
D. The conduction of a control element is varied to maintain a constant output voltage

A

D. The conduction of a control element is varied to maintain a constant output voltage

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43
Q

“What is a characteristic of a switching electronic voltage regulator?”

A. The resistance of a control element is varied in direct proportion to the line voltage or load current
B. It is generally less efficient than a linear regulator
C. The controlled device’s duty cycle is changed to produce a constant average output voltage
D. It gives a ramp voltage at its output

A

C. The controlled device’s duty cycle is changed to produce a constant average output voltage

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44
Q

“What device is typically used as a stable voltage reference in a linear voltage regulator?”

A. A Zener diode
B. A tunnel diode
C. An SCR
D. A varactor diode

A

A. A Zener diode

45
Q

“Which of the following types of linear voltage regulator usually make the most efficient use of the primary power source?”

A. A series current source
B. A series regulator
C. A shunt regulator
D. A shunt current source

A

B. A series regulator

46
Q

“Which of the following types of linear voltage regulator places a constant load on the unregulated voltage source?”

A. A constant current source
B. A series regulator
C. A shunt current source
D. A shunt regulator

A

D. A shunt regulator

47
Q

“What is the purpose of Q1 in the circuit shown in Figure E7-2?”

A. It provides negative feedback to improve regulation
B. It provides a constant load for the voltage source
C. It controls the current supplied to the load
D. It provides D1 with current

A

C. It controls the current supplied to the load

48
Q

“What is the purpose of C2 in the circuit shown in Figure E7-2?”

A. It bypasses rectifier output ripple around D1
B. It is a brute force filter for the output
C. To self-resonate at the hum frequency
D. To provide fixed DC bias for Q1

A

A. It bypasses rectifier output ripple around D1

49
Q

“What type of circuit is shown in Figure E7-2?”

A. Switching voltage regulator
B. Grounded emitter amplifier
C. Linear voltage regulator
D. Monostable multivibrator

A

C. Linear voltage regulator

50
Q

“What is the main reason to use a charge controller with a solar power system?”

A. Prevention of battery undercharge
B. Control of electrolyte levels during battery discharge
C. Prevention of battery damage due to overcharge
D. Matching of day and night charge rates

A

C. Prevention of battery damage due to overcharge

51
Q

“What is the primary reason that a high-frequency switching type high-voltage power supply can be both less expensive and lighter in weight than a conventional power supply?”

A. The inverter design does not require any output filtering
B. It uses a diode bridge rectifier for increased output
C. The high frequency inverter design uses much smaller transformers and filter components for an equivalent power output
D. It uses a large power factor compensation capacitor to recover power from the unused portion of the AC cycle

A

C. The high frequency inverter design uses much smaller transformers and filter components for an equivalent power output

52
Q

“What is the function of the pass transistor in a linear voltage regulator circuit?”

A. Permits a wide range of output voltage settings
B. Provides a stable input impedance over a wide range of source voltage
C. Maintains nearly constant output impedance over a wide range of load current
D. Maintains nearly constant output voltage over a wide range of load current

A

D. Maintains nearly constant output voltage over a wide range of load current

53
Q

“What is the dropout voltage of an analog voltage regulator?”

A. Minimum input voltage for rated power dissipation
B. Maximum output voltage drops when the input voltage is varied over its specified range
C. Minimum input-to-output voltage required to maintain regulation
D. Maximum that the output voltage may decrease at rated load

A

C. Minimum input-to-output voltage required to maintain regulation

54
Q

“What is the equation for calculating power dissipated by a series linear voltage regulator?”

A. Input voltage multiplied by input current
B. Input voltage divided by output current
C. Voltage difference from input to output multiplied by output current
D. Output voltage multiplied by output current

A

C. Voltage difference from input to output multiplied by output current

55
Q

“What is the purpose of connecting equal-value resistors across power supply filter capacitors connected in series?”

A. Equalize the voltage across each capacitor
B. Discharge the capacitors when voltage is removed
C. Provide a minimum load on the supply
D. All these choices are correct

A

D. All these choices are correct

56
Q

“What is the purpose of a step-start circuit in a high-voltage power supply?”

A. To provide a dual-voltage output for reduced power applications
B. To compensate for variations of the incoming line voltage
C. To allow for remote control of the power supply
D. To allow the filter capacitors to charge gradually

A

D. To allow the filter capacitors to charge gradually

57
Q

“Which of the following can be used to generate FM phone emissions?”

A. A balanced modulator on the audio amplifier
B. A reactance modulator on the oscillator
C. A reactance modulator on the final amplifier
D. A balanced modulator on the oscillator

A

B. A reactance modulator on the oscillator

58
Q

“What is the function of a reactance modulator?”

A. To produce PM signals by using an electrically variable resistance
B. To produce AM signals by using an electrically variable inductance or capacitance
C. To produce AM signals by using an electrically variable resistance
D. To produce PM or FM signals by using an electrically variable inductance or capacitance

A

D. To produce PM or FM signals by using an electrically variable inductance or capacitance

59
Q

“What is a frequency discriminator stage in a FM receiver?”

A. An FM generator circuit
B. A circuit for filtering two closely adjacent signals
C. An automatic band-switching circuit
D. A circuit for detecting FM signals

A

D. A circuit for detecting FM signals

60
Q

“What is one way a single-sideband phone signal can be generated?”

A. By using a balanced modulator followed by a filter
B. By using a reactance modulator followed by a mixer
C. By using a loop modulator followed by a mixer
D. By driving a product detector with a DSB signal

A

A. By using a balanced modulator followed by a filter

61
Q

“What circuit is added to an FM transmitter to boost the higher audio frequencies?”

A. A de-emphasis network
B. A heterodyne suppressor
C. A heterodyne enhancer
D. A pre-emphasis network

A

D. A pre-emphasis network

62
Q

“Why is de-emphasis commonly used in FM communications receivers?”

A. For compatibility with transmitters using phase modulation
B. To reduce impulse noise reception
C. For higher efficiency
D. To remove third-order distortion products

A

A. For compatibility with transmitters using phase modulation

63
Q

“What is meant by the term “baseband” in radio communications?”

A. The lowest frequency band that the transmitter or receiver covers
B. The frequency range occupied by a message signal prior to modulation
C. The unmodulated bandwidth of the transmitted signal
D. The basic oscillator frequency in an FM transmitter that is multiplied to increase the deviation and carrier frequency

A

B. The frequency range occupied by a message signal prior to modulation

64
Q

“What are the principal frequencies that appear at the output of a mixer circuit?”

A. Two and four times the original frequency
B. The square root of the product of input frequencies
C. The two input frequencies along with their sum and difference frequencies
D. 1.414 and 0.707 times the input frequency

A

C. The two input frequencies along with their sum and difference frequencies

65
Q

“What occurs when an excessive amount of signal energy reaches a mixer circuit?”

A. Spurious mixer products are generated
B. Mixer blanking occurs
C. Automatic limiting occurs
D. A beat frequency is generated

A

A. Spurious mixer products are generated

66
Q

“How does a diode envelope detector function?”

A. By rectification and filtering of RF signals
B. By breakdown of the Zener voltage
C. By mixing signals with noise in the transition region of the diode
D. By sensing the change of reactance in the diode with respect to frequency

A

A. By rectification and filtering of RF signals

67
Q

“Which type of detector circuit is used for demodulating SSB signals?”

A. Discriminator
B. Phase detector
C. Product detector
D. Phase comparator

A

C. Product detector

68
Q

“What is meant by direct digital conversion as applied to software defined radios?”

A. Software is converted from source code to object code during operation of the receiver
B. Incoming RF is converted to a control voltage for a voltage controlled oscillator
C. Incoming RF is digitized by an analog-to-digital converter without being mixed with a local oscillator signal
D. A switching mixer is used to generate I and Q signals directly from the RF input

A

C. Incoming RF is digitized by an analog-to-digital converter without being mixed with a local oscillator signal

69
Q

“What kind of digital signal processing audio filter is used to remove unwanted noise from a received SSB signal?”

A. An adaptive filter
B. A crystal-lattice filter
C. A Hilbert-transform filter
D. A phase-inverting filter

A

A. An adaptive filter

70
Q

“What type of digital signal processing filter is used to generate an SSB signal?”

A. An adaptive filter
B. A notch filter
C. A Hilbert-transform filter
D. An elliptical filter

A

C. A Hilbert-transform filter

71
Q

“What is a common method of generating an SSB signal using digital signal processing?”

A. Mixing products are converted to voltages and subtracted by adder circuits
B. A frequency synthesizer removes the unwanted sidebands
C. Varying quartz crystal characteristics emulated in digital form
D. Signals are combined in quadrature phase relationship

A

D. Signals are combined in quadrature phase relationship

72
Q

“How frequently must an analog signal be sampled by an analog-to-digital converter so that the signal can be accurately reproduced?”

A. At least half the rate of the highest frequency component of the signal
B. At least twice the rate of the highest frequency component of the signal
C. At the same rate as the highest frequency component of the signal
D. At four times the rate of the highest frequency component of the signal

A

B. At least twice the rate of the highest frequency component of the signal

73
Q

“What is the minimum number of bits required for an analog-to-digital converter to sample a signal with a range of 1 volt at a resolution of 1 millivolt?”

A. 4 bits
B. 6 bits
C. 8 bits
D. 10 bits

A

D. 10 bits

74
Q

“What function is performed by a Fast Fourier Transform?”

A. Converting analog signals to digital form
B. Converting digital signals to analog form
C. Converting digital signals from the time domain to the frequency domain
D. Converting 8-bit data to 16-bit data

A

C. Converting digital signals from the time domain to the frequency domain

75
Q

“What is the function of decimation?”

A. Converting data to binary code decimal form
B. Reducing the effective sample rate by removing samples
C. Attenuating the signal
D. Removing unnecessary significant digits

A

B. Reducing the effective sample rate by removing samples

76
Q

“Why is an anti-aliasing digital filter required in a digital decimator?”

A. It removes high-frequency signal components that would otherwise be reproduced as lower frequency components
B. It peaks the response of the decimator, improving bandwidth
C. It removes low-frequency signal components to eliminate the need for DC restoration
D. It notches out the sampling frequency to avoid sampling errors

A

A. It removes high-frequency signal components that would otherwise be reproduced as lower frequency components

77
Q

“What aspect of receiver analog-to-digital conversion determines the maximum receive bandwidth of a Direct Digital Conversion SDR?”

A. Sample rate
B. Sample width in bits
C. Sample clock phase noise
D. Processor latency

A

A. Sample rate

78
Q

“What sets the minimum detectable signal level for a direct-sampling SDR receiver in the absence of atmospheric or thermal noise?”

A. Sample clock phase noise
B. Reference voltage level and sample width in bits
C. Data storage transfer rate
D. Missing codes and jitter

A

B. Reference voltage level and sample width in bits

79
Q

“Which of the following is an advantage of a Finite Impulse Response (FIR) filter vs an Infinite Impulse Response (IIR) digital filter?”

A. FIR filters can delay all frequency components of the signal by the same amount
B. FIR filters are easier to implement for a given set of passband rolloff requirements
C. FIR filters can respond faster to impulses
D. All these choices are correct

A

A. FIR filters can delay all frequency components of the signal by the same amount

80
Q

“What is the function of taps in a digital signal processing filter?”

A. To reduce excess signal pressure levels
B. Provide access for debugging software
C. Select the point at which baseband signals are generated
D. Provide incremental signal delays for filter algorithms

A

D. Provide incremental signal delays for filter algorithms

81
Q

“Which of the following would allow a digital signal processing filter to create a sharper filter response?”

A. Higher data rate
B. More taps
C. Complex phasor representations
D. Double-precision math routines

A

B. More taps

82
Q

“What is the typical output impedance of an op-amp?”

A. Very low
B. Very high
C. 100 ohms
D. 1000 ohms

A

A. Very low

83
Q

“What is ringing in a filter?”

A. An echo caused by a long time delay
B. A reduction in high frequency response
C. Partial cancellation of the signal over a range of frequencies
D. Undesired oscillations added to the desired signal

A

D. Undesired oscillations added to the desired signal

84
Q

“What is the typical input impedance of an op-amp?”

A. 100 ohms
B. 1000 ohms
C. Very low
D. Very high

A

D. Very high

85
Q

“What is meant by the term “op-amp input offset voltage”?”

A. The output voltage of the op-amp minus its input voltage
B. The difference between the output voltage of the op-amp and the input voltage required in the immediately following stage
C. The differential input voltage needed to bring the open loop output voltage to zero
D. The potential between the amplifier input terminals of the op-amp in an open loop condition

A

C. The differential input voltage needed to bring the open loop output voltage to zero

86
Q

“How can unwanted ringing and audio instability be prevented in an op-amp RC audio filter circuit?”

A. Restrict both gain and Q
B. Restrict gain but increase Q
C. Restrict Q but increase gain
D. Increase both gain and Q

A

A. Restrict both gain and Q

87
Q

“What is the gain-bandwidth of an operational amplifier?”

A. The maximum frequency for a filter circuit using that type of amplifier
B. The frequency at which the open-loop gain of the amplifier equals one
C. The gain of the amplifier at a filter’s cutoff frequency
D. The frequency at which the amplifier’s offset voltage is zero

A

B. The frequency at which the open-loop gain of the amplifier equals one

88
Q

“What magnitude of voltage gain can be expected from the circuit in Figure E7 3 when R1 is 10 ohms and RF is 470 ohms?”

A. 0.21
B. 94
C. 47
D. 24

A

C. 47

89
Q

“How does the gain of an ideal operational amplifier vary with frequency?”

A. It increases linearly with increasing frequency
B. It decreases linearly with increasing frequency
C. It decreases logarithmically with increasing frequency
D. It does not vary with frequency

A

D. It does not vary with frequency

90
Q

“What will be the output voltage of the circuit shown in Figure E7-3 if R1 is 1000 ohms, RF is 10,000 ohms, and 0.23 volts DC is applied to the input?”

A. 0.23 volts
B. 2.3 volts
C. -0.23 volts
D. -2.3 volts

A

D. -2.3 volts

91
Q

“What absolute voltage gain can be expected from the circuit in Figure E7-3 when R1 is 1800 ohms and RF is 68 kilohms?”

A. 1
B. 0.03
C. 38
D. 76

A

C. 38

92
Q

“What absolute voltage gain can be expected from the circuit in Figure E7-3 when R1 is 3300 ohms and RF is 47 kilohms?”

A. 28
B. 14
C. 7
D. 0.07

A

B. 14

93
Q

“What is an operational amplifier?”

A. A high-gain, direct-coupled differential amplifier with very high input impedance and very low output impedance
B. A digital audio amplifier whose characteristics are determined by components external to the amplifier
C. An amplifier used to increase the average output of frequency modulated amateur signals to the legal limit
D. A RF amplifier used in the UHF and microwave regions

A

A. A high-gain, direct-coupled differential amplifier with very high input impedance and very low output impedance

94
Q

“What are three oscillator circuits used in amateur radio equipment?”

A. Taft, Pierce and negative feedback
B. Pierce, Fenner and Beane
C. Taft, Hartley and Pierce
D. Colpitts, Hartley and Pierce

A

D. Colpitts, Hartley and Pierce

95
Q

“What is a microphonic?”

A. An IC used for amplifying microphone signals
B. Distortion caused by RF pickup on the microphone cable
C. Changes in oscillator frequency due to mechanical vibration
D. Excess loading of the microphone by an oscillator

A

C. Changes in oscillator frequency due to mechanical vibration

96
Q

“How is positive feedback supplied in a Hartley oscillator?”

A. Through a tapped coil
B. Through a capacitive divider
C. Through link coupling
D. Through a neutralizing capacitor

A

A. Through a tapped coil

97
Q

“How is positive feedback supplied in a Colpitts oscillator?”

A. Through a tapped coil
B. Through link coupling
C. Through a capacitive divider
D. Through a neutralizing capacitor

A

C. Through a capacitive divider

98
Q

“How is positive feedback supplied in a Pierce oscillator?”

A. Through a tapped coil
B. Through link coupling
C. Through a neutralizing capacitor
D. Through a quartz crystal

A

D. Through a quartz crystal

99
Q

“Which of the following oscillator circuits are commonly used in VFOs?”

A. Pierce and Zener
B. Colpitts and Hartley
C. Armstrong and deForest
D. Negative feedback and balanced feedback

A

B. Colpitts and Hartley

100
Q

“How can an oscillator’s microphonic responses be reduced?”

A. Use NP0 capacitors
B. Reduce noise on the oscillator’s power supply
C. Increase the bias voltage
D. Mechanically isolate the oscillator circuitry from its enclosure

A

D. Mechanically isolate the oscillator circuitry from its enclosure

101
Q

“Which of the following components can be used to reduce thermal drift in crystal oscillators?”

A. NP0 capacitors
B. Toroidal inductors
C. Wirewound resistors
D. Non-inductive resistors

A

A. NP0 capacitors

102
Q

“What type of frequency synthesizer circuit uses a phase accumulator, lookup table, digital to analog converter, and a low-pass anti-alias filter?”

A. A direct digital synthesizer
B. A hybrid synthesizer
C. A phase-locked loop synthesizer
D. A diode-switching matrix synthesizer

A

A. A direct digital synthesizer

103
Q

“What information is contained in the lookup table of a direct digital synthesizer (DDS)?”

A. The phase relationship between a reference oscillator and the output waveform
B. Amplitude values that represent the desired waveform
C. The phase relationship between a voltage-controlled oscillator and the output waveform
D. Frequently used receiver and transmitter frequencies

A

B. Amplitude values that represent the desired waveform

104
Q

“What are the major spectral impurity components of direct digital synthesizers?”

A. Broadband noise
B. Digital conversion noise
C. Spurious signals at discrete frequencies
D. Nyquist limit noise

A

C. Spurious signals at discrete frequencies

105
Q

“Which of the following must be done to ensure that a crystal oscillator provides the frequency specified by the crystal manufacturer?”

A. Provide the crystal with a specified parallel inductance
B. Provide the crystal with a specified parallel capacitance
C. Bias the crystal at a specified voltage
D. Bias the crystal at a specified current

A

B. Provide the crystal with a specified parallel capacitance

106
Q

“Which of the following is a technique for providing highly accurate and stable oscillators needed for microwave transmission and reception?”

A. Use a GPS signal reference
B. Use a rubidium stabilized reference oscillator
C. Use a temperature-controlled high Q dielectric resonator
D. All these choices are correct

A

D. All these choices are correct

107
Q

“What is a phase-locked loop circuit?”

A. An electronic servo loop consisting of a ratio detector, reactance modulator, and voltage-controlled oscillator
B. An electronic circuit also known as a monostable multivibrator
C. An electronic servo loop consisting of a phase detector, a low-pass filter, a voltage-controlled oscillator, and a stable reference oscillator
D. An electronic circuit consisting of a precision push-pull amplifier with a differential input

A

C. An electronic servo loop consisting of a phase detector, a low-pass filter, a voltage-controlled oscillator, and a stable reference oscillator

108
Q

“Which of these functions can be performed by a phase-locked loop?”

A. Wide-band AF and RF power amplification
B. Comparison of two digital input signals, digital pulse counter
C. Photovoltaic conversion, optical coupling
D. Frequency synthesis, FM demodulation

A

D. Frequency synthesis, FM demodulation

Amateur Radio 2024 - Extra (10 decks)

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