E7 Practical Circuits Flashcards
1
Q
E7A01 (C) Which is a bi-stable circuit?
A
C. A flip-flop
2
Q
E7A02 (A) What is the function of a decade counter digital IC?
A
A. It produces one output pulse for every ten input pulses
3
Q
E7A03 (B) Which of the following can divide the frequency of a pulse train by 2?
A
B. A flip-flop
4
Q
E7A04 (B) How many flip-flops are required to divide a signal frequency by 4?
A
B. 2
5
Q
E7A05 (D) Which of the following is a circuit that continuously alternates between two states without an external clock?
A
D. Astable multivibrator
6
Q
E7A06 (A) What is a characteristic of a monostable multivibrator?
A
A. It switches momentarily to the opposite binary state and then returns to its original state after a set time
7
Q
E7A07 (D) What logical operation does a NAND gate perform?
A
D. It produces logic “0” at its output only when all inputs are logic “1”
8
Q
E7A08 (A) What logical operation does an OR gate perform?
A
A. It produces logic “1” at its output if any or all inputs are logic “1”
9
Q
E7A09 (C) What logical operation is performed by an exclusive NOR gate?
A
C. It produces logic “0” at its output if any single input is logic “1”
10
Q
E7A10 (C) What is a truth table?
A
C. A list of inputs and corresponding outputs for a digital device
11
Q
E7A11 (D) What type of logic defines “1” as a high voltage?
A
D. Positive Logic
12
Q
E7A12 (C) What type of logic defines “0” as a high voltage?
A
C. Negative logic
13
Q
E7B01 (A) For what portion of a signal cycle does a Class AB amplifier operate?
A
A. More than 180 degrees but less than 360 degrees
14
Q
E7B02 (A) What is a Class D amplifier?
A
A. A type of amplifier that uses switching technology to achieve high efficiency
15
Q
E7B03 (A) Which of the following components form the output of a class D amplifier circuit?
A
A. A low-pass filter to remove switching signal components
16
Q
E7B04 (A) Where on the load line of a Class A common emitter amplifier would bias normally be set?
A
A. Approximately half-way between saturation and cutoff
17
Q
E7B05 (C) What can be done to prevent unwanted oscillations in an RF power amplifier?
A
C. Install parasitic suppressors and/or neutralize the stage
18
Q
E7B06 (B) Which of the following amplifier types reduces or eliminates even order harmonics?
A
B. Push-pull
19
Q
E7B07 (D) Which of the following is a likely result when a Class C amplifier is used to amplify a single-sideband phone signal?
A
D. Signal distortion and excessive bandwidth
20
Q
E7B08 (C) How can an RF power amplifier be neutralized?
A
C. By feeding a 180-degree out-of-phase portion of the output back to the input
21
Q
E7B09 (D) 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
D. The tuning capacitor is adjusted for minimum plate current, and the loading capacitor is adjusted for maximum permissible plate current
22
Q
E7B10 (B) In Figure E7-1, what is the purpose of R1 and R2?
A
B. Fixed bias
23
Q
E7B11 (D) In Figure E7-1, what is the purpose of R3?
A
D. Self bias
24
Q
E7B12 (C) What type of amplifier circuit is shown in Figure E7-1?
A
C. Common emitter
25
E7B13 (A) In Figure E7-2, what is the purpose of R?
A. Emitter load
26
E7B14 (B) Why are switching amplifiers more efficient than linear amplifiers?
B. The power transistor is at saturation or cut off most of the time, resulting in low power dissipation
27
E7B15 (C) What is one way to prevent thermal runaway in a bipolar transistor amplifier?
C. Use a resistor in series with the emitter
28
E7B16 (A) What is the effect of intermodulation products in a linear power amplifier?
A. Transmission of spurious signals
29
E7B17 (A) 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
30
E7B18 (C) What is a characteristic of a grounded-grid amplifier?
C. Low input impedance
31
E7C01 (D) How are the capacitors and inductors of a low-pass filter Pi-network arranged between the network's 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
32
E7C02 (C) Which of the following is a property of a T-network with series capacitors and a parallel shunt inductor?
C. It is a high-pass filter
33
E7C03 (A) What advantage does a Pi-L-network have over a regular Pi-network for impedance matching between the final amplifier of a vacuum-tube transmitter and an antenna?
A. Greater harmonic suppression
34
E7C04 (C) How does an impedance-matching circuit transform a complex impedance to a resistive impedance?
C. It cancels the reactive part of the impedance and changes the resistive part to a desired value
35
E7C05 (D) Which filter type is described as having ripple in the passband and a sharp cutoff?
D. A Chebyshev filter
36
E7C06 (C) What are the distinguishing features of an elliptical filter?
C. Extremely sharp cutoff with one or more notches in the stop band
37
E7C07 (B) What kind of filter would you use to attenuate an interfering carrier signal while receiving an SSB transmission?
B. A notch filter
38
E7C08 (A) Which of the following factors has the greatest effect in helping determine the bandwidth and response shape of a crystal ladder filter?
A. The relative frequencies of the individual crystals
39
E7C09 (B) What is a Jones filter as used as part of an HF receiver IF stage?
B. A variable bandwidth crystal lattice filter
40
E7C10 (B) Which of the following filters would be the best choice for use in a 2 meter repeater duplexer?
B. A cavity filter
41
E7C11 (D) Which of the following is the common name for a filter network which is equivalent to two L-networks connected back-to-back with the two inductors in series and the capacitors in shunt at the input and output?
D. Pi
42
E7C12 (B) Which describes a Pi-L-network used for matching a vacuum tube final amplifier to a 50 ohm unbalanced output?
B. A Pi-network with an additional series inductor on the output
43
E7C13 (A) 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 varied depending on the component values chosen
44
E7C14 (C) Which mode is most affected by non-linear phase response in a receiver IF filter?
C. Digital
45
E7C15 (D) What is a crystal lattice filter?
D. A filter with narrow bandwidth and steep skirts made using quartz crystals
46
E7D01 (D) What is one characteristic of a linear electronic voltage regulator?
D. The conduction of a control element is varied to maintain a constant output voltage
47
E7D02 (C) What is one characteristic of a switching electronic voltage regulator?
C. The controlled device’s duty cycle is changed to produce a constant average output voltage
48
E7D03 (A) What device is typically used as a stable reference voltage in a linear voltage regulator?
A. A Zener diode
49
E7D04 (B) Which of the following types of linear voltage regulator usually make the most efficient use of the primary power source?
B. A series regulator
50
E7D05 (D) Which of the following types of linear voltage regulator places a constant load on the unregulated voltage source?
D. A shunt regulator
51
E7D06 (C) What is the purpose of Q1 in the circuit shown in Figure E7-3?
C. It increases the current-handling capability of the regulator
52
E7D07 (A) What is the purpose of C2 in the circuit shown in Figure E7-3?
A. It bypasses hum around D1
53
E7D08 (C) What type of circuit is shown in Figure E7-3?
C. Linear voltage regulator
54
E7D09 (C) What is the main reason to use a charge controller with a solar power system?
C. Prevention of battery damage due to overcharge
55
E7D10 (C) 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?
C. The high frequency inverter design uses much smaller transformers and filter components for an equivalent power output
56
E7D11 (D) What circuit element is controlled by a series analog voltage regulator to maintain a constant output voltage?
D. Pass transistor
57
E7D12 (C) What is the drop-out voltage of an analog voltage regulator?
C. Minimum input-to-output voltage required to maintain regulation
58
E7D13 (C) What is the equation for calculating power dissipation by a series connected linear voltage regulator?
C. Voltage difference from input to output multiplied by output current
59
E7D14 (C) What is one purpose of a "bleeder" resistor in a conventional unregulated power supply?
C. To improve output voltage regulation
60
E7D15 (D) What is the purpose of a "step-start" circuit in a high voltage power supply?
D. To allow the filter capacitors to charge gradually
61
E7D16 (D) When several electrolytic filter capacitors are connected in series to increase the operating voltage of a power supply filter circuit, why should resistors be connected across each capacitor?
A. To equalize, as much as possible, the voltage drop across each capacitor B. To provide a safety bleeder to discharge the capacitors when the supply is off C. To provide a minimum load current to reduce voltage excursions at light loads D. All of these choices are correct
62
E7E01 (B) Which of the following can be used to generate FM phone emissions?
B. A reactance modulator on the oscillator
63
E7E02 (D) What is the function of a reactance modulator?
D. To produce PM signals by using an electrically variable inductance or capacitance
64
E7E03 (C) How does an analog phase modulator function?
C. By varying the tuning of an amplifier tank circuit to produce PM signals
65
E7E04 (A) What is one way a single-sideband phone signal can be generated?
A. By using a balanced modulator followed by a filter
66
E7E05 (D) What circuit is added to an FM transmitter to boost the higher audio frequencies?
D. A pre-emphasis network
67
E7E06 (A) Why is de-emphasis commonly used in FM communications receivers?
A. For compatibility with transmitters using phase modulation
68
E7E07 (B) What is meant by the term baseband in radio communications?
B. The frequency components present in the modulating signal
69
E7E08 (C) What are the principal frequencies that appear at the output of a mixer circuit?
C. The two input frequencies along with their sum and difference frequencies
70
E7E09 (A) What occurs when an excessive amount of signal energy reaches a mixer circuit?
A. Spurious mixer products are generated
71
E7E10 (A) How does a diode detector function?
A. By rectification and filtering of RF signals
72
E7E11 (C) Which type of detector is used for demodulating SSB signals?
C. Product detector
73
E7E12 (D) What is a frequency discriminator stage in a FM receiver?
D. A circuit for detecting FM signals
74
E7F01 (C) What is meant by direct digital conversion as applied to software defined radios?
C. Incoming RF is digitized by an analog-to-digital converter without being mixed with a local oscillator signal
75
E7F02 (A) What kind of digital signal processing audio filter is used to remove unwanted noise from a received SSB signal?
A. An adaptive filter
76
E7F03 (C) What type of digital signal processing filter is used to generate an SSB signal?
C. A Hilbert-transform filter
77
E7F04 (D) What is a common method of generating an SSB signal using digital signal processing?
D. Combine signals with a quadrature phase relationship
78
E7F05 (B) How frequently must an analog signal be sampled by an analog-to-digital converter so that the signal can be accurately reproduced?
B. At twice the rate of the highest frequency component of the signal
79
E7F06 (D) 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?
D. 10 bits
80
E7F07 (C) What function can a Fast Fourier Transform perform?
C. Converting digital signals from the time domain to the frequency domain
81
E7F08 (B) What is the function of decimation with regard to digital filters?
B. Reducing the effective sample rate by removing samples
82
E7F09 (A) Why is an anti-aliasing digital filter required in a digital decimator?
A. It removes high-frequency signal components which would otherwise be reproduced as lower frequency components
83
E7F10 (A) What aspect of receiver analog-to-digital conversion determines the maximum receive bandwidth of a Direct Digital Conversion SDR?
A. Sample rate
84
E7F11 (B) What sets the minimum detectable signal level for an SDR in the absence of atmospheric or thermal noise?
B. Reference voltage level and sample width in bits
85
E7F12 (A) What digital process is applied to I and Q signals in order to recover the baseband modulation information?
A. Fast Fourier Transform
86
E7F13 (D) What is the function of taps in a digital signal processing filter?
D. Provide incremental signal delays for filter algorithms
87
E7F14 (B) Which of the following would allow a digital signal processing filter to create a sharper filter response?
B. More taps
88
E7F15 (A) 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 delay all frequency components of the signal by the same amount
89
E7F16 (D) How might the sampling rate of an existing digital signal be adjusted by a factor of 3/4?
D. Interpolate by a factor of three, then decimate by a factor of four
90
E7F17 (D) What do the letters I and Q in I/Q Modulation represent?
D. In-phase and Quadrature
91
E7G01 (A) What is the typical output impedance of an integrated circuit op-amp?
A. Very low
92
E7G02 (D) What is the effect of ringing in a filter?
D. Undesired oscillations added to the desired signal
93
E7G03 (D) What is the typical input impedance of an integrated circuit op-amp?
D. Very high
94
E7G04 (C) What is meant by the term op-amp input offset voltage?`
C. The differential input voltage needed to bring the open loop output voltage to zero
95
E7G05 (A) How can unwanted ringing and audio instability be prevented in a multi-section op-amp RC audio filter circuit?
A. Restrict both gain and Q
96
E7G06 (D) Which of the following is the most appropriate use of an op-amp active filter?
D. As an audio filter in a receiver
97
E7G07 (C) What magnitude of voltage gain can be expected from the circuit in Figure E7-4 when R1 is 10 ohms and RF is 470 ohms?
C. 47
98
E7G08 (D) How does the gain of an ideal operational amplifier vary with frequency?
D. It does not vary with frequency
99
E7G09 (D) What will be the output voltage of the circuit shown in Figure E7-4 if R1 is 1000 ohms, RF is 10,000 ohms, and 0.23 volts DC is applied to the input?
D. -2.3 volts
100
E7G10 (C) What absolute voltage gain can be expected from the circuit in Figure E7-4 when R1 is 1800 ohms and RF is 68 kilohms?
C. 38
101
E7G11 (B) What absolute voltage gain can be expected from the circuit in Figure E7-4 when R1 is 3300 ohms and RF is 47 kilohms?
B. 14
102
E7G12 (A) What is an integrated circuit operational amplifier?
A. A high-gain, direct-coupled differential amplifier with very high input impedance and very low output impedance
103
E7H01 (D) What are three oscillator circuits used in Amateur Radio equipment?
D. Colpitts, Hartley and Pierce
104
E7H02 (C) Which describes a microphonic?
C. Changes in oscillator frequency due to mechanical vibration
105
E7H03 (A) How is positive feedback supplied in a Hartley oscillator?
A. Through a tapped coil
106
E7H04 (C) How is positive feedback supplied in a Colpitts oscillator?
C. Through a capacitive divider
107
E7H05 (D) How is positive feedback supplied in a Pierce oscillator?
D. Through a quartz crystal
108
E7H06 (B) Which of the following oscillator circuits are commonly used in VFOs?
B. Colpitts and Hartley
109
E7H07 (D) How can an oscillator’s microphonic responses be reduced?
D. Mechanically isolating the oscillator circuitry from its enclosure
110
E7H08 (A) Which of the following components can be used to reduce thermal drift in crystal oscillators?
A. NP0 capacitors
111
E7H09 (A) 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
112
E7H10 (B) What information is contained in the lookup table of a direct digital frequency synthesizer?
B. The amplitude values that represent a sine-wave output
113
E7H11 (C) What are the major spectral impurity components of direct digital synthesizers?
C. Spurious signals at discrete frequencies
114
E7H12 (B) Which of the following must be done to insure that a crystal oscillator provides the frequency specified by the crystal manufacturer?
B. Provide the crystal with a specified parallel capacitance
115
E7H13 (D) 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 of these choices are correct
116
E7H14 (C) What is a phase-locked loop circuit?
C. An electronic servo loop consisting of a phase detector, a low-pass filter, a voltage-controlled oscillator, and a stable reference oscillator
117
E7H15 (D) Which of these functions can be performed by a phase-locked loop?
D. Frequency synthesis, FM demodulation
