Which circuit is bistable?
CA flip-flop
extra pool
Subelement E7 question review
All 99 official questions with the exact winning phrase marked.
What is the function of a decade counter?
AIt produces one output pulse for every 10 input pulses
Which of the following can divide the frequency of a pulse train by 2?
BA flip-flop
How many flip-flops are required to divide a signal frequency by 16?
A4
Which of the following circuits continuously alternates between two states without an external clock signal?
DAstable multivibrator
What is a characteristic of a monostable multivibrator?
AIt switches temporarily to an alternate state for a set time
What logical operation does a NAND gate perform?
DIt produces a 0 at its output only if all inputs are 1
What logical operation does an OR gate perform?
AIt produces a 1 at its output if any input is 1
What logical operation is performed by a two-input exclusive NOR gate?
CIt produces a 0 at its output if one and only one of its inputs is 1
What is a truth table?
BA list of inputs and corresponding outputs for a digital device
What does “positive logic” mean in reference to logic devices?
BHigh voltage represents a 1, low voltage a 0
For what portion of the signal cycle does each active element in a push-pull, Class AB amplifier conduct?
AMore than 180 degrees but less than 360 degrees
What is a Class D amplifier?
AAn amplifier that uses switching technology to achieve high efficiency
What circuit is required at the output of an RF switching amplifier?
AA filter to remove harmonic content
What is the operating point of a Class A common emitter amplifier?
AApproximately halfway between saturation and cutoff
What can be done to prevent unwanted oscillations in an RF power amplifier?
CInstall parasitic suppressors and/or neutralize the stage
What is a characteristic of a grounded-grid amplifier?
BLow input impedance
Which of the following is the likely result of using a Class C amplifier to amplify a single-sideband phone signal?
DSignal distortion and excessive bandwidth
Why are switching amplifiers more efficient than linear amplifiers?
BThe switching device is at saturation or cutoff most of the time
What is characteristic of an emitter follower (or common collector) amplifier?
DInput and output signals in-phase
In Figure E7-1, what is the purpose of R1 and R2?
BVoltage divider bias
In Figure E7-1, what is the purpose of R3?
DSelf bias
What type of amplifier circuit is shown in Figure E7-1?
CCommon emitter
How are the capacitors and inductors of a low-pass filter Pi-network arranged between the network’s input and output?
DA capacitor is connected between the input and ground, another capacitor is connected between the output and ground, and an inductor is connected between the input and output
What is the frequency response of a T-network with series capacitors and a shunt inductor?
BHigh-pass
What is the purpose of adding an inductor to a Pi-network to create a Pi-L-network?
AGreater harmonic suppression
How does an impedance-matching circuit transform a complex impedance to a resistive impedance?
CIt cancels the reactive part of the impedance and changes the resistive part to the desired value
Which filter type has ripple in the passband and a sharp cutoff?
DA Chebyshev filter
What are the characteristics of an elliptical filter?
CExtremely sharp cutoff with one or more notches in the stop band
Which describes a Pi-L network?
BA Pi-network with an additional output series inductor
Which of the following is most frequently used as a band-pass or notch filter in VHF and UHF transceivers?
BA helical filter
What is a crystal lattice filter?
DA filter for low-level signals made using quartz crystals
Which of the following filters is used in a 2-meter band repeater duplexer?
BA cavity filter
Which of the following measures a filter’s ability to reject signals in adjacent channels?
CShape factor
How does a linear electronic voltage regulator work?
DThe conduction of a control element is varied to maintain a constant output voltage
How does a switchmode voltage regulator work?
BBy varying the duty cycle of pulses input to a filter
What device is used as a stable voltage reference?
AA Zener diode
Which of the following describes a three-terminal voltage regulator?
BA series regulator
Which of the following types of linear voltage regulator operates by loading the unregulated voltage source?
DA shunt regulator
What is the purpose of Q1 in the circuit shown in Figure E7-2?
CIt controls the current to keep the output voltage constant
What is the purpose of C2 in the circuit shown in Figure E7-2?
AIt bypasses rectifier output ripple around D1
What type of circuit is shown in Figure E7-2?
CLinear voltage regulator
How is battery operating time calculated?
CCapacity in amp-hours divided by average current
Why is a switching type power supply less expensive and lighter than an equivalent linear power supply?
CThe high frequency inverter design uses much smaller transformers and filter components for an equivalent power output
What is the purpose of an inverter connected to a solar panel output?
DConvert the panel’s output from DC to AC
What is the dropout voltage of a linear voltage regulator?
CMinimum input-to-output voltage required to maintain regulation
Which of the following calculates power dissipated by a series linear voltage regulator?
CVoltage difference from input to output multiplied by output current
What is the purpose of connecting equal-value resistors across power supply filter capacitors connected in series?
DAll these choices are correct
What is the purpose of a step-start circuit in a high-voltage power supply?
DTo allow the filter capacitors to charge gradually
Which of the following can be used to generate FM phone signals?
BReactance modulation of a local oscillator
What is the function of a reactance modulator?
DProduce PM or FM signals by varying a capacitance
What is a frequency discriminator?
DA circuit for detecting FM signals
What is one way to produce a single-sideband phone signal?
AUse a balanced modulator followed by a filter
What is added to an FM speech channel to boost the higher audio frequencies?
DA pre-emphasis network
Why is de-emphasis used in FM communications receivers?
AFor compatibility with transmitters using phase modulation
What is meant by the term “baseband” in radio communications?
BThe frequency range occupied by a message signal prior to modulation
What are the principal frequencies that appear at the output of a mixer?
CThe two input frequencies along with their sum and difference frequencies
What occurs when the input signal levels to a mixer are too high?
ASpurious mixer products are generated
How does a diode envelope detector function?
ABy rectification and filtering of RF signals
Which type of detector is used for demodulating SSB signals?
CProduct detector
What is meant by “direct sampling” in software defined radios?
CIncoming RF is digitized by an analog-to-digital converter without being mixed with a local oscillator signal
What kind of digital signal processing audio filter is used to remove unwanted noise from a received SSB signal?
AAn adaptive filter
What type of digital signal processing filter is used to generate an SSB signal?
CA Hilbert-transform filter
Which method generates an SSB signal using digital signal processing?
DSignals are combined in quadrature phase relationship
How frequently must an analog signal be sampled to be accurately reproduced?
BAt least twice the rate of the highest frequency component of the signal
What is the minimum number of bits required to sample a signal with a range of 1 volt at a resolution of 1 millivolt?
D10 bits
What function is performed by a Fast Fourier Transform?
CConverting signals from the time domain to the frequency domain
What is the function of decimation?
BReducing the effective sample rate by removing samples
Why is an anti-aliasing filter required in a decimator?
AIt removes high-frequency signal components that would otherwise be reproduced as lower frequency components
What aspect of receiver analog-to-digital conversion determines the maximum receive bandwidth of a direct-sampling software defined radio (SDR)?
ASample rate
What sets the minimum detectable signal level for a direct-sampling software defined receiver in the absence of atmospheric or thermal noise?
BReference voltage level and sample width in bits
Which of the following is generally true of Finite Impulse Response (FIR) filters?
AFIR filters can delay all frequency components of the signal by the same amount
What is the function of taps in a digital signal processing filter?
DProvide incremental signal delays for filter algorithms
Which of the following would allow a digital signal processing filter to create a sharper filter response?
BMore taps
What is the typical output impedance of an op-amp?
AVery low
What is the frequency response of the circuit in E7-3 if a capacitor is added across the feedback resistor?
BLow-pass filter
What is the typical input impedance of an op-amp?
DVery high
What is meant by the term “op-amp input offset voltage”?
CThe differential input voltage needed to bring the open loop output voltage to zero
How can unwanted ringing and audio instability be prevented in an op-amp audio filter?
ARestrict both gain and Q
What is the gain-bandwidth of an operational amplifier?
BThe frequency at which the open-loop gain of the amplifier equals one
What voltage gain can be expected from the circuit in Figure E7-3 when R1 is 10 ohms and RF is 470 ohms?
C47
How does the gain of an ideal operational amplifier vary with frequency?
DIt does not vary with frequency
What will be the output voltage of the circuit shown in Figure E7-3 if R1 is 1,000 ohms, RF is 10,000 ohms, and 0.23 volts DC is applied to the input?
D-2.3 volts
What absolute voltage gain can be expected from the circuit in Figure E7-3 when R1 is 1,800 ohms and RF is 68 kilohms?
C38
What absolute voltage gain can be expected from the circuit in Figure E7-3 when R1 is 3,300 ohms and RF is 47 kilohms?
B14
What is an operational amplifier?
AA high-gain, direct-coupled differential amplifier with very high input impedance and very low output impedance
What are three common oscillator circuits?
DColpitts, Hartley, and Pierce
What is a microphonic?
CChanges in oscillator frequency caused by mechanical vibration
What is a phase-locked loop?
CAn electronic servo loop consisting of a phase detector, a low-pass filter, a voltage-controlled oscillator, and a stable reference oscillator
How is positive feedback supplied in a Colpitts oscillator?
CThrough a capacitive divider
How is positive feedback supplied in a Pierce oscillator?
DThrough a quartz crystal
Which of these functions can be performed by a phase-locked loop?
BFrequency synthesis and FM demodulation
How can an oscillator’s microphonic responses be reduced?
DMechanically isolate the oscillator circuitry from its enclosure
Which of the following components can be used to reduce thermal drift in crystal oscillators?
ANP0 capacitors
What type of frequency synthesizer circuit uses a phase accumulator, lookup table, digital-to-analog converter, and a low-pass anti-alias filter?
AA direct digital synthesizer
What information is contained in the lookup table of a direct digital synthesizer (DDS)?
BAmplitude values that represent the desired waveform
What are the major spectral impurity components of direct digital synthesizers?
CSpurious signals at discrete frequencies
Which of the following ensures that a crystal oscillator operates on the frequency specified by the crystal manufacturer?
BProvide the crystal with a specified parallel capacitance
Which of the following is a technique for providing highly accurate and stable oscillators needed for microwave transmission and reception?
DAll these choices are correct