Amateur Extra Class Exam Question Pool- Subelement E-6
Subelement E-1 Subelement E-2 Subelement E-3 Subbelement E-4 Subelement E-5
Subelement E-6 Subelement E-7 Subelement E-8 Subbelement E-9 Subelement E-0
SUBELEMENT E6 - CIRCUIT COMPONENTS [6 Exam Questions - 6 Groups]
E6A - Semiconductor materials and devices: semiconductor materials; germanium, silicon, P-type, N-type; transistor types: NPN, PNP, junction, field-effect transistors: enhancement mode; depletion mode; MOS; CMOS; N-channel; P-channel
In what application is gallium arsenide used as a semiconductor material?
A. In high-current rectifier circuits
B. In high-power audio circuits
C. In microwave circuits
D. In very low-frequency RF circuits
Which of the following semiconductor materials contains excess free electrons?
D. Insulated gate
Why does a PN-junction diode not conduct current when reverse biased?
A. Only P-type semiconductor material can conduct current
B. Only N-type semiconductor material can conduct current
C. Holes in P-type material and electrons in the N-type material are separated by the applied voltage, widening the depletion region
D. Excess holes in P-type material combine with the electrons in N-type material, converting the entire diode into an insulator
What is the name given to an impurity atom that adds holes to a semiconductor crystal structure?
A. Insulator impurity
B. N-type impurity
C. Acceptor impurity
D. Donor impurity
How does DC input impedance at the gate of a field-effect transistor compare with the DC input impedance of a bipolar transistor?
A. They are both low impedance
B. An FET has lower input impedance
C. An FET has higher input impedance
D. They are both high impedance
What is the beta of a bipolar junction transistor?
A. The frequency at which the current gain is reduced to 0.707
B. The change in collector current with respect to base current
C. The breakdown voltage of the base to collector junction
D. The switching speed
Which of the following indicates that a silicon NPN junction transistor is biased on?
A. Base-to-emitter resistance of approximately 6 to 7 ohms
B. Base-to-emitter resistance of approximately 0.6 to 0.7 ohms
C. Base-to-emitter voltage of approximately 6 to 7 volts
D. Base-to-emitter voltage of approximately 0.6 to 0.7 volts
What term indicates the frequency at which the grounded-base current gain of a transistor has decreased to 0.7 of the gain obtainable at 1 kHz?
A. Corner frequency
B. Alpha rejection frequency
C. Beta cutoff frequency
D. Alpha cutoff frequency
What is a depletion-mode FET?
A. An FET that exhibits a current flow between source and drain when no gate voltage is applied
B. An FET that has no current flow between source and drain when no gate voltage is applied
C. Any FET without a channel
D. Any FET for which holes are the majority carriers
In Figure E6-1, what is the schematic symbol for an N-channel dual-gate MOSFET?
In Figure E6-1, what is the schematic symbol for a P-channel junction FET?
Why do many MOSFET devices have internally connected Zener diodes on the gates?
A. To provide a voltage reference for the correct amount of reverse-bias gate voltage
B. To protect the substrate from excessive voltages
C. To keep the gate voltage within specifications and prevent the device from overheating
D. To reduce the chance of static damage to the gate
E6B - Diodes
What is the most useful characteristic of a Zener diode?
A. A constant current drop under conditions of varying voltage
B. A constant voltage drop under conditions of varying current
C. A negative resistance region
D. An internal capacitance that varies with the applied voltage
What is an important characteristic of a Schottky diode as compared to an ordinary silicon diode when used as a power supply rectifier?
A. Much higher reverse voltage breakdown
B. More constant reverse avalanche voltage
C. Longer carrier retention time
D. Less forward voltage drop
What type of bias is required for an LED to emit light?
A. Reverse bias
B. Forward bias
C. Zero bias
D. Inductive bias
What type of semiconductor device is designed for use as a voltage-controlled capacitor?
A. Varactor diode
B. Tunnel diode
C. Silicon-controlled rectifier
D. Zener diode
What characteristic of a PIN diode makes it useful as an RF switch?
A. Extremely high reverse breakdown voltage
B. Ability to dissipate large amounts of power
C. Reverse bias controls its forward voltage drop
D. Low junction capacitance
Which of the following is a common use of a Schottky diode?
A. As a rectifier in high current power supplies
B. As a variable capacitance in an automatic frequency control circuit
C. As a constant voltage reference in a power supply
D. As a VHF/UHF mixer or detector
What is the failure mechanism when a junction diode fails due to excessive current?
A. Excessive inverse voltage
B. Excessive junction temperature
C. Insufficient forward voltage
D. Charge carrier depletion
Which of the following is a Schottky barrier diode?
A. Metal-semiconductor junction
B. Electrolytic rectifier
C. PIN junction
D. Thermionic emission diode
What is a common use for point-contact diodes?
A. As a constant current source
B. As a constant voltage source
C. As an RF detector
D. As a high-voltage rectifier
In Figure E6-2, what is the schematic symbol for a light-emitting diode?
What is used to control the attenuation of RF signals by a PIN diode?
A. Forward DC bias current
B. A sub-harmonic pump signal
C. Reverse voltage larger than the RF signal
D. Capacitance of an RF coupling capacitor
E6C - Digital ICs: Families of digital ICs; gates; Programmable Logic Devices (PLDs)
What is the function of hysteresis in a comparator?
A. To prevent input noise from causing unstable output signals
B. To allow the comparator to be used with AC input signals
C. To cause the output to change states continually
D. To increase the sensitivity
What happens when the level of a comparator’s input signal crosses the threshold?
A. The IC input can be damaged
B. The comparator changes its output state
C. The comparator enters latch-up
D. The feedback loop becomes unstable
What is tri-state logic?
A. Logic devices with 0, 1, and high-impedance output states
B. Logic devices that utilize ternary math
C. Low-power logic devices designed to operate at 3 volts
D. Proprietary logic devices manufactured by Tri-State Devices
Which of the following is an advantage of BiCMOS logic?
A. Its simplicity results in much less expensive devices than standard CMOS
B. It is immune to electrostatic damage
C. It has the high input impedance of CMOS and the low output impedance of bipolar transistors
D. All these choices are correct
What is an advantage of CMOS logic devices over TTL devices?
A. Differential output capability
B. Lower distortion
C. Immune to damage from static discharge
D. Lower power consumption
Why do CMOS digital integrated circuits have high immunity to noise on the input signal or power supply?
A. Large bypass capacitance is inherent
B. The input switching threshold is about two times the power supply voltage
C. The input switching threshold is about one-half the power supply voltage
D. Bandwidth is very limited
What best describes a pull-up or pull-down resistor?
A. A resistor in a keying circuit used to reduce key clicks
B. A resistor connected to the positive or negative supply line used to establish a voltage when an input or output is an open circuit
C. A resistor that ensures that an oscillator frequency does not drift
D. A resistor connected to an op-amp output that prevents signals from exceeding the power supply voltage
In Figure E6-3, what is the schematic symbol for a NAND gate?
What is a Programmable Logic Device (PLD)?
A. A logic circuit that can be modified during use
B. A programmable collection of logic gates and circuits in a single integrated circuit
C. Programmable equipment used for testing digital logic integrated circuits
D. A type of transistor whose gain can be changed by digital logic circuits
In Figure E6-3, what is the schematic symbol for a NOR gate?
In Figure E6-3, what is the schematic symbol for the NOT operation (inverter)?
E6D - Toroidal and Solenoidal Inductors: permeability, core material, selecting, winding; transformers; piezoelectric devices
Why should core saturation of an impedance matching transformer be avoided?
A. Harmonics and distortion could result
B. Magnetic flux would increase with frequency
C. RF susceptance would increase
D. Temporary changes of the core permeability could result
What is the equivalent circuit of a quartz crystal?
A. Motional capacitance, motional inductance, and loss resistance in series, all in parallel with a shunt capacitor representing electrode and stray capacitance
B. Motional capacitance, motional inductance, loss resistance, and a capacitor representing electrode and stray capacitance all in parallel
C. Motional capacitance, motional inductance, loss resistance, and a capacitor representing electrode and stray capacitance all in series
D. Motional inductance and loss resistance in series, paralleled with motional capacitance and a capacitor representing electrode and stray capacitance
Which of the following is an aspect of the piezoelectric effect?
A. Mechanical deformation of material by the application of a voltage
B. Mechanical deformation of material by the application of a magnetic field
C. Generation of electrical energy in the presence of light
D. Increased conductivity in the presence of light
Which materials are commonly used as a core in an inductor?
A. Polystyrene and polyethylene
B. Ferrite and brass
C. Teflon and Delrin
D. Cobalt and aluminum
What is one reason for using ferrite cores rather than powdered iron in an inductor?
A. Ferrite toroids generally have lower initial permeability
B. Ferrite toroids generally have better temperature stability
C. Ferrite toroids generally require fewer turns to produce a given inductance value
D. Ferrite toroids are easier to use with surface mount technology
What core material property determines the inductance of an inductor?
A. Thermal impedance
What is current in the primary winding of a transformer called if no load is attached to the secondary?
A. Magnetizing current
B. Direct current
C. Excitation current
D. Stabilizing current
What is one reason for using powdered-iron cores rather than ferrite cores in an inductor?
A. Powdered-iron cores generally have greater initial permeability
B. Powdered-iron cores generally maintain their characteristics at higher currents
C. Powdered-iron cores generally require fewer turns to produce a given inductance
D. Powdered-iron cores use smaller diameter wire for the same inductance
What devices are commonly used as VHF and UHF parasitic suppressors at the input and output terminals of a transistor HF amplifier?
A. Electrolytic capacitors
B. Butterworth filters
C. Ferrite beads
D. Steel-core toroids
What is a primary advantage of using a toroidal core instead of a solenoidal core in an inductor?
A. Toroidal cores confine most of the magnetic field within the core material
B. Toroidal cores make it easier to couple the magnetic energy into other components
C. Toroidal cores exhibit greater hysteresis
D. Toroidal cores have lower Q characteristics
Which type of core material decreases inductance when inserted into a coil?
D. Powdered iron
What is inductor saturation?
A. The inductor windings are over-coupled
B. The inductor’s voltage rating is exceeded causing a flashover
C. The ability of the inductor’s core to store magnetic energy has been exceeded
D. Adjacent inductors become over-coupled
What is the primary cause of inductor self-resonance?
A. Inter-turn capacitance
B. The skin effect
C. Inductive kickback
D. Non-linear core hysteresis
E6E - Analog ICs: MMICs, IC packaging characteristics
Why is gallium arsenide (GaAs) useful for semiconductor devices operating at UHF and higher frequencies?
A. Higher noise figures
B. Higher electron mobility
C. Lower junction voltage drop
D. Lower transconductance
Which of the following device packages is a through-hole type?
C. Ball grid array
Which of the following materials is likely to provide the highest frequency of operation when used in MMICs?
B. Silicon nitride
C. Silicon dioxide
D. Gallium nitride
Which is the most common input and output impedance of circuits that use MMICs?
A. 50 ohms
B. 300 ohms
C. 450 ohms
D. 10 ohms
Which of the following noise figure values is typical of a low-noise UHF preamplifier?
A. 2 dB
B. -10 dB
C. 44 dBm
D. -20 dBm
What characteristics of the MMIC make it a popular choice for VHF through microwave circuits?
A. The ability to retrieve information from a single signal even in the presence of other strong signals
B. Plate current that is controlled by a control grid
C. Nearly infinite gain, very high input impedance, and very low output impedance
D. Controlled gain, low noise figure, and constant input and output impedance over the specified frequency range
What type of transmission line is used for connections to MMICs?
A. Miniature coax
B. Circular waveguide
C. Parallel wire
How is power supplied to the most common type of MMIC?
A. Through a resistor and/or RF choke connected to the amplifier output lead
B. MMICs require no operating bias
C. Through a capacitor and RF choke connected to the amplifier input lead
D. Directly to the bias voltage (VCC IN) lead
Which of the following component package types would be most suitable for use at frequencies above the HF range?
B. Axial lead
C. Radial lead
D. Surface mount
What advantage does surface-mount technology offer at RF compared to using through-hole components?
A. Smaller circuit area
B. Shorter circuit-board traces
C. Components have less parasitic inductance and capacitance
D. All these choices are correct
What is a characteristic of DIP packaging used for integrated circuits?
A. Package mounts in a direct inverted position
B. Low leakage doubly insulated package
C. Two chips in each package (Dual In Package)
D. A total of two rows of connecting pins placed on opposite sides of the package (Dual In-line Package)
Why are DIP through-hole package ICs not typically used at UHF and higher frequencies?
A. Too many pins
B. Epoxy coating is conductive above 300 MHz
C. Excessive lead length
D. Unsuitable for combining analog and digital signals
E6F - Electro-optical technology: photoconductivity; photovoltaic devices; optical sensors and encoders; optical isolation
What absorbs the energy from light falling on a photovoltaic cell?
What happens to the conductivity of a photoconductive material when light shines on it?
A. It increases
B. It decreases
C. It stays the same
D. It becomes unstable
What is the most common configuration of an optoisolator or optocoupler?
A. A lens and a photomultiplier
B. A frequency modulated helium-neon laser
C. An amplitude modulated helium-neon laser
D. An LED and a phototransistor
What is the photovoltaic effect?
A. The conversion of voltage to current when exposed to light
B. The conversion of light to electrical energy
C. The conversion of electrical energy to mechanical energy
D. The tendency of a battery to discharge when exposed to light
Which describes an optical shaft encoder?
A. A device that detects rotation of a control by interrupting a light source with a patterned wheel
B. A device that measures the strength of a beam of light using analog to digital conversion
C. A digital encryption device often used to encrypt spacecraft control signals
D. A device for generating RTTY signals by means of a rotating light source
Which of these materials is most commonly used to create photoconductive devices?
A. A crystalline semiconductor
B. An ordinary metal
C. A heavy metal
D. A liquid semiconductor
What is a solid-state relay?
A. A relay using transistors to drive the relay coil
B. A device that uses semiconductors to implement the functions of an electromechanical relay
C. A mechanical relay that latches in the on or off state each time it is pulsed
D. A semiconductor passive delay line
Why are optoisolators often used in conjunction with solid-state circuits when switching 120 VAC?
A. Optoisolators provide a low impedance link between a control circuit and a power circuit
B. Optoisolators provide impedance matching between the control circuit and power circuit
C. Optoisolators provide a very high degree of electrical isolation between a control circuit and the circuit being switched
D. Optoisolators eliminate the effects of reflected light in the control circuit
What is the efficiency of a photovoltaic cell?
A. The output RF power divided by the input DC power
B. Cost per kilowatt-hour generated
C. The open-circuit voltage divided by the short-circuit current under full illumination
D. The relative fraction of light that is converted to current
What is the most common type of photovoltaic cell used for electrical power generation?
C. Cadmium Sulfide
D. Copper oxide
What is the approximate open-circuit voltage produced by a fully illuminated silicon photovoltaic cell?
A. 0.1 V
B. 0.5 V
C. 1.5 V
D. 12 V