4 Semiconductor Devices MaterialsElectrons in outer shell are called valence electrons.Valence electrons interact with other atoms to form compounds.Atoms want to have their outer shell of electrons filled.Full shell = 8 electrons.Atoms can share valence electrons with other atoms to fill their outer shell forming a compound.
5 Semiconductor Devices MaterialsAtoms with fewer than 4 valence electrons are normally conductors (metals).Atoms with more than 4 valence electrons are normally non-conductors.Atoms with 4 valence electrons are normally semi-conductors.SiliconGermanium
6 Semiconductor Devices MaterialsAtoms can arrange themselves into a regular pattern by sharing valence electrons to form a crystal.Crystals of pure silicon (Si) or germanium (Ge) are not normally good conductors.
7 Semiconductor Devices MaterialsCrystals of pure semi-conductor atoms, such as silicon (Si), can have a precisely controlled number of other atoms inserted into the crystal structure.This process is called “doping”.Doping with atoms with 3 or 5 valence electrons causes the crystal to become more conductive.
8 Semiconductor Devices MaterialsAdding an element with 5 valence electrons (donor impurity) creates N-type material.Excess free electrons.Typical donor impurities:ArsenicAntimonyPhosphorus
9 Semiconductor Devices MaterialsAdding an element with 3 valence electrons (acceptor impurity) creates P-type material.Shortage of free electrons (holes).Typical acceptor impurities:AluminumGalliumIndium
10 Semiconductor Devices MaterialsMajority Charge Carriers.N-Type Material = ElectronP-Type Material = HoleOther semiconductor materials.Gallium-Arsenide (GaAs).LED’sMicrowave frequencies.Gallium-Arsenide-Phosphide (GaAsP).
11 E6A01 -- In what application is gallium arsenide used as a semiconductor material in preference to germanium or silicon?In high-current rectifier circuitsIn high-power audio circuitsAt microwave frequenciesAt very low frequency RF circuits
12 E6A02 -- Which of the following semiconductor materials contains excess free electrons? N-typeP-typeBipolarInsulated gate
13 E6A03 -- What are the majority charge carriers in P-type semiconductor material? Free neutronsFree protonsHolesFree electrons
14 E6A04 -- What is the name given to an impurity atom that adds holes to a semiconductor crystal structure?Insulator impurityN-type impurityAcceptor impurityDonor impurity
15 E6A15 -- Which of the following semiconductor materials contains an excess of holes in the outer shell of electrons?N-typeP-typeSuperconductor-typeBipolar-type
16 E6A16 -- What are the majority charge carriers in N-type semiconductor material? HolesFree electronsFree protonsFree neutrons
17 Semiconductor Devices DiodesA diode allows current flow in one direction and resists current flow in the other direction.Two terminals:AnodeCathode.Electrons flow from cathode to anode.Holes flow from anode to cathode.
18 Semiconductor Devices DiodesJunction diodes.With no voltage applied, electrons & holes combine at the junction forming a depletion region.
19 Semiconductor Devices DiodesDiode Ratings.Peak Inverse Voltage (PIV).Avalanche voltage.Maximum Average Forward Current.Maximum Allowable Junction Temperature.Forward Voltage Drop.Silicon = 0.7 Volts (approx.)Germanium = 0.3 Volts (approx.)GaAs & GaAsP = 1.2 Volts to 1.5 Volts (approx.)
20 Semiconductor Devices DiodesSchottky Barrier Diodes.P-type material replaced with a layer of metal.Point-Contact Diodes.Hot-Carrier Diodes.Lower forward voltage drop.Less power dissipation.Power supplies.
21 Semiconductor Devices DiodesPoint-Contact Diodes.Very low junction capacitance.Very low current.Better for VHF & UHF detectors than normal junction diode.
22 Semiconductor Devices DiodesHot-Carrier Diodes.Similar to point-contact diode.More stable mechanically.Lower contact resistance Higher current capability.
23 Semiconductor Devices DiodesZener Diodes.Operates with reverse bias.Operates at avalanche voltage.Large change in avalanche current results in small change in voltage.Designed to withstand avalanche current with proper heat sink.
24 Semiconductor Devices DiodesTunnel Diodes.Special type of diode that does not rectify.When properly biased, exhibits negative resistance.Once used for oscillators & amplifiers at microwave frequencies.
25 Semiconductor Devices DiodesVaractor Diodes (VariCap).Operates with reverse bias.Varying voltage varies junction capacitance.A few picofarads to >100 pF.Used for variable-frequency oscillators & for FM modulators.
26 Semiconductor Devices DiodesPIN Diodes.3rd layer of undoped(intrinsic) material.Forward resistance varies with forward bias voltage.More voltage lower resistance.Used for RF attenuation & switching.
27 E6B01 -- What is the most useful characteristic of a Zener diode? A constant current drop under conditions of varying voltageA constant voltage drop under conditions of varying currentA negative resistance regionAn internal capacitance that varies with the applied voltage
28 E6B02 -- What is an important characteristic of a Schottky diode as compared to an ordinary silicon diode when used as a power supply rectifier?Much higher reverse voltage breakdownControlled reverse avalanche voltageEnhanced carrier retention timeLess forward voltage drop
29 E6B03 -- What special type of diode is capable of both amplification and oscillation? Point contactZenerTunnelJunction
30 E6B04 -- What type of semiconductor device is designed for use as a voltage-controlled capacitor? Varactor diodeTunnel diodeSilicon-controlled rectifierZener diode
31 E6B05 -- What characteristic of a PIN diode makes it useful as an RF switch or attenuator? Extremely high reverse breakdown voltageAbility to dissipate large amounts of powerReverse bias controls its forward voltage dropA large region of intrinsic material
32 E6B06 -- Which of the following is a common use of a hot-carrier diode? As balanced mixers in FM generationAs a variable capacitance in an automatic frequency control circuitAs a constant voltage reference in a power supplyAs a VHF / UHF mixer or detector
33 E6B07 -- What is the failure mechanism when a junction diode fails due to excessive current? Excessive inverse voltageExcessive junction temperatureInsufficient forward voltageCharge carrier depletion
34 E6B08 -- Which of the following describes a type of semiconductor diode? Metal-semiconductor junctionElectrolytic rectifierCMOS-field effectThermionic emission diode
35 E6B09 -- What is a common use for point contact diodes? As a constant current sourceAs a constant voltage sourceAs an RF detectorAs a high voltage rectifier
36 E6B11 -- What is used to control the attenuation of RF signals by a PIN diode? Forward DC bias currentA sub-harmonic pump signalReverse voltage larger than the RF signalCapacitance of an RF coupling capacitor
37 E6B12 -- What is one common use for PIN diodes? As a constant current sourceAs a constant voltage sourceAs an RF switchAs a high voltage rectifier
39 Semiconductor Devices Bipolar TransistorsBase region very thin.Base-emitter junction is forward biased.Collector-base junction is reverse biased.A small current flowing through base-emitter junction causes a large current to flow through the collector-base junction.Low input impedance.Low output impedance.
41 Semiconductor Devices Bipolar TransistorsTransistor characteristics.Alpha Cut-off Frequency.Frequency at which current gain drops to times the value at 1 kHz.Practical upper frequency limit for common-base amplifier.Beta Cut-off Frequency.Practical upper frequency limit for common-emitter amplifier.
42 E6A05 -- What is the alpha of a bipolar junction transistor? The change of collector current with respect to base currentThe change of base current with respect to collector currentThe change of collector current with respect to emitter currentThe change of collector current with respect to gate current
43 E6A06 -- What is the beta of a bipolar junction transistor? The frequency at which the current gain is reduced to 1The change in collector current with respect to base currentThe breakdown voltage of the base to collector junctionThe switching speed of the transistor
44 E6A07 -- In Figure E6-1, what is the schematic symbol for a PNP transistor? 245
45 E6A08 -- 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?Corner frequencyAlpha rejection frequencyBeta cutoff frequencyAlpha cutoff frequency
46 Semiconductor Devices Field-Effect Transistors (FET)Gate voltage controls channel current.Gain measured in transconductance.G = ID / VGSiemensHigh input impedance.2 ModesEnhancement ModeDepletion Mode
48 Semiconductor Devices Field-Effect TransistorsJunction Field-Effect Transistor (JFET).A reverse-biased voltage between the gate & source controls the source-drain current.Gate terminal is always reverse-biased.Very little gate current flow.High input impedance.Low output impedance.
50 Semiconductor Devices Field-Effect TransistorsMetal Oxide Semiconductor Field-Effect Transistor (MOSFET).Gate is insulated from the source-drain channel.No gate current flow.Very high input impedance.≥10 megohms.Low output impedance.Susceptible to damage from static discharge.Often have internal zener diodes to protect gate.
52 Semiconductor Devices Field-Effect TransistorsEnhancement and depletion mode FET’s.Enhancement mode.VG = 0 VDC No source-drain current flow.Increasing gate voltage larger source-drain current.Depletion mode.VG = 0 VDC Non-zero source-drain current flow.Increasing gate voltage smaller source-drain current.
53 E6A09 -- What is a depletion-mode FET? An FET that exhibits a current flow between source and drain when no gate voltage is appliedAn FET that has no current flow between source and drain when no gate voltage is appliedAny FET without a channelAny FET for which holes are the majority carriers
54 E6A10 -- In Figure E6-2, what is the schematic symbol for an N-channel dual-gate MOSFET? 456
55 E6A11 -- In Figure E6-2, what is the schematic symbol for a P-channel junction FET? 36
56 E6A12 -- Why do many MOSFET devices have internally connected Zener diodes on the gates? To provide a voltage reference for the correct amount of reverse-bias gate voltageTo protect the substrate from excessive voltagesTo keep the gate voltage within specifications and prevent the device from overheatingTo reduce the chance of the gate insulation being punctured by static discharges or excessive voltages
57 E6A14 -- How does DC input impedance at the gate of a field-effect transistor compare with the DC input impedance of a bipolar transistor?They are both low impedanceAn FET has low input impedance; a bipolar transistor has high input impedanceAn FET has high input impedance; a bipolar transistor has low input impedanceThey are both high impedance
58 E6A17 -- What are the names of the three terminals of a field-effect transistor? Gate 1, gate 2, drainEmitter, base, collectorEmitter, base 1, base 2Gate, drain, source
60 E6E04 -- What is the most common input and output impedance of circuits that use MMICs? 50 ohms300 ohms450 ohms10 ohms
61 E6E05 -- Which of the following noise figure values is typical of a low-noise UHF preamplifier? 2 dB-10 dB44 dBm-20 dBm
62 E6E06 -- What characteristics of the MMIC make it a popular choice for VHF through microwave circuits?The ability to retrieve information from a single signal even in the presence of other strong signals.Plate current that is controlled by a control gridNearly infinite gain, very high input impedance, and very low output impedanceControlled gain, low noise figure, and constant input and output impedance over the specified frequency range
63 E6E07 -- Which of the following is typically used to construct a MMIC-based microwave amplifier? Ground-plane constructionMicrostrip constructionPoint-to-point constructionWave-soldering construction
64 E6E08 -- How is power-supply voltage normally furnished to the most common type of monolithic microwave integrated circuit (MMIC)?Through a resistor and/or RF choke connected to the amplifier output leadMMICs require no operating biasThrough a capacitor and RF choke connected to the amplifier input leadDirectly to the bias-voltage (VCC IN) lead
65 E6E11 -- Which of the following materials is likely to provide the highest frequency of operation when used in MMICs?SiliconSilicon nitrideSilicon dioxideGallium nitride
67 Display Devices Light-Emitting Diodes (LED) Emit light when forward-biased.Forward voltage drop varies with color.Red – 1.6 VoltsYellow – 2 VoltsGreen – 4 VoltsTypically 10 mA to 20 mA for full brightness.
68 Display Devices Light-Emitting Diodes (LED) Red, green, & yellow. Gallium-Arsenide, Gallium-Phosphide, or a combination.Blue.Silicon-Carbide or Zinc-SelenideWhite.Actually blue LED’s with yellow phosphor coating on lens.
69 E6B10 -- In Figure E6-3, what is the schematic symbol for a light-emitting diode? 567
70 E6B13 -- What type of bias is required for an LED to emit light? Reverse biasForward biasZero biasInductive bias
71 Display Devices Liquid-Crystal Displays Rotates polarization of light passing through it.Applying voltage across crystal changes polarization.
72 Display Devices Liquid-Crystal Displays Advantages Disadvantages Very low power required.Low operating voltage.Thin.DisadvantagesLow temperatures affect speed of polarization shift.May be damaged by high temperatures.May be difficult to read in bright light or at an angle.
73 E6D05 -- What is a liquid-crystal display (LCD)? A modern replacement for a quartz crystal oscillator which displays its fundamental frequencyA display using a crystalline liquid which, in conjunction with polarizing filters, becomes opaque when voltage is appliedA frequency-determining unit for a transmitter or receiverA display that uses a glowing liquid to remain brightly lit in dim light
74 E6D15 -- What is the principle advantage of liquid-crystal display (LCD) devices over other types of display devices?They consume less powerThey can display changes instantlyThey are visible in all light conditionsThey can be easily interchanged with other display devices
76 Display Devices Cathode-Ray Tubes An electron bean is accelerated by a high voltage & strikes a glass surface coated with a phosphorescent material.Phosphorescent coating glows when struck by electrons.More electrons brighter glow.Persistence is length of time glow continues after electrons no longer strike the coating.Electron beam is deflected from side-to-side & top-to-bottom to paint desired image.
79 Display Devices Cathode-Ray Tubes Electrostatic deflection. More precise deflection of electron beam.Better for high-frequency displays.Oscilloscopes.Test equipment.
80 Display Devices Cathode-Ray Tubes Increasing anode voltage increases speed of electrons.Higher speed increased brightness.Higher speed decreased image size.Excessive speed can generate x-rays.
81 E6D01 -- What is cathode ray tube (CRT) persistence? The time it takes for an image to appear after the electron beam is turned onThe relative brightness of the display under varying conditions of ambient lightThe ability of the display to remain in focus under varying conditionsThe length of time the image remains on the screen after the beam is turned off
82 E6D02 -- Exceeding what design rating can cause a cathode ray tube (CRT) to generate X-rays? The heater voltageThe anode voltageThe operating temperatureThe operating frequency
83 E6D13 -- What type of CRT deflection is better when high-frequency waveforms are to be displayed on the screen?ElectromagneticTubularRadarElectrostatic
84 Display Devices Charge-Coupled Devices Combines digital & analog signal processing.Array of capacitors with MOSFET switches on input & output.Basis of nearly all modern cameras, both still & video.
85 Display Devices Charge-Coupled Devices Series of “buckets” containing an analog voltage.Analog values transferred from “bucket” to “bucket” when a clock pulse is received.Can NOT be used as an analog-to-digital converter.
86 E6D03 -- Which of the following is true of a charge-coupled device (CCD)? Its phase shift changes rapidly with frequencyIt is a CMOS analog-to-digital converterIt samples an analog signal and passes it in stages from the input to the outputIt is used in a battery charger circuit
87 E6D04 -- What function does a charge-coupled device (CCD) serve in a modern video camera? It stores photogenerated charges as signals corresponding to pixelsIt generates the horizontal pulses needed for electron beam scanningIt focuses the light used to produce a pattern of electrical charges corresponding to the imageIt combines audio and video information to produce a composite RF signal
88 E6D14 -- Which is NOT true of a charge-coupled device (CCD)? It uses a combination of analog and digital circuitryIt can be used to make an audio delay lineIt is commonly used as an analog-to-digital converterIt samples and stores analog signals
90 Digital Logic Logic Basics Combinational logic. Boolean Algebra. Output state determined by combination of input states.Boolean Algebra.Variables have only 2 values.0 or 1.False or True.Off or On.Truth table.
91 Digital Logic Logic Basics One-input elements. Non-inverting buffer. Inverting buffer or “Not” gate.AB1AB1
92 Digital Logic Logic Basics AND gate. Output true only if ALL inputs are true.ABC1ABC1
93 Digital Logic Logic Basics OR gate. Output true if one or more of the inputs are true.ABC1ABC1
94 Digital Logic Logic Basics Exclusive OR gate. Output true if one and only one of the inputs is true.ABC1ABC1
95 Digital Logic Logic Basics Positive & negative logic. Positive logic. True represented by highest voltage.Negative logic.True represented by lowest voltage.Positive logic NAND functionally equivalent to negative logic NOR (same truth table).
96 Digital Logic Tri-State Logic Allows multiple devices to be connected in parallel on same output bus.InputOutputEnableorSelect
97 Digital Logic Logic Basics Tri-state logic. Three output states. Low (0).High (1).Off (high impedance).Allows multiple devices to be connected in parallel on same output bus.Only one device can be “on” at a time.All others MUST be in the high-impedance state.
98 E6C03 -- Which of the following describes tri-state logic? Logic devices with 0, 1, and high impedance output statesLogic devices that utilize ternary mathLow power logic devices designed to operate at 3 voltsProprietary logic devices manufactured by Tri-State Devices
99 E6C04 -- Which of the following is the primary advantage of tri-state logic? Low power consumptionAbility to connect many device outputs to a common busHigh speed operationMore efficient arithmetic operations
100 E6C07 -- In Figure E6-5, what is the schematic symbol for an AND gate? 1234
101 E6C08 -- In Figure E6-5, what is the schematic symbol for a NAND gate? 1234
102 E6C09 -- In Figure E6-5, what is the schematic symbol for an OR gate? 2346
103 E6C10 -- In Figure E6-5, what is the schematic symbol for a NOR gate? 234
104 E6C11 -- In Figure E6-5, what is the schematic symbol for the NOT operation (inverter)? 2456
105 E7A07 -- What logical operation does a NAND gate perform? It produces a logic "0" at its output only when all inputs are logic "0“It produces a logic "1" at its output only when all inputs are logic "1“It produces a logic "0" at its output if some but not all of its inputs are logic "1“It produces a logic "0" at its output only when all inputs are logic "1“
106 E7A08 -- What logical operation does an OR gate perform? It produces a logic "1" at its output if any or all inputs are logic "1“It produces a logic "0" at its output if all inputs are logic "1“It only produces a logic "0" at its output when all inputs are logic "1“It produces a logic "1" at its output if all inputs are logic "0”
107 E7A09 -- What logical operation is performed by a two-input exclusive NOR gate? It produces a logic "0" at its output only if all inputs are logic "0“It produces a logic "1" at its output only if all inputs are logic "1“It produces a logic "0" at its output if any single input is a logic “1”It produces a logic "1" at its output if any single input is a logic “1”
108 E7A10 -- What is a truth table? A table of logic symbols that indicate the high logic states of an op-ampA diagram showing logic states when the digital device's output is trueA list of inputs and corresponding outputs for a digital deviceA table of logic symbols that indicates the low logic states of an op-amp
109 E7A11 -- What is the name for logic which represents a logic "1" as a high voltage? Reverse LogicAssertive LogicNegative logicPositive Logic
110 E7A12 -- What is the name for logic which represents a logic "0" as a high voltage? Reverse LogicAssertive LogicNegative logicPositive Logic
111 Digital Logic Synchronous Logic Sequential logic Current state dependent on both current inputs and previous state.Must include some form of “memory”.
112 Digital Logic Synchronous Logic Flip-flops. a.k.a -- Bi-stable multivibrator, latch.Several different types.S-R, J-K, D, T.Gated, non-gated.Clocked, non-clocked.Can be used as frequency divider.
113 Digital Logic Synchronous Logic Synchronous and asynchronous flip-flops.Synchronous flip-flops.Clock input.Changes state ONLY at time determined by clock input.Asynchronous flip-flops.No clock input.Changes state whenever any input changes state.
114 Digital Logic Synchronous Logic Dynamic versus static inputs. Dynamic inputs.a.k.a. – Edge-triggered.Flip-flop acts ONLY when clock input changes state.Positive-edge triggered.Negative-edge triggered.Static inputs.a.k.a. – Level-triggered.Flip-flop acts when any input changes state.
115 Digital Logic Synchronous Logic Set-Reset (SR) Latch Most basic latch type.SRActionNo change1Q = 0Q = 1Forbidden
116 Digital Logic Synchronous Logic Gated SR Latch Same as SR latch with enable input.ESRAction?No change1Q = 0Q = 1Forbidden
117 Digital Logic Synchronous Logic J-K flip-flop Adds toggle function to SR latch.Must be clocked.Clock (>)JKAction--No change1Q = 0Q = 1Toggle (Q = not Q)
118 Digital Logic Synchronous Logic Frequency divider. Cascaded J-K flip-flops.
119 Digital Logic Synchronous Logic D flip-flop Most common type. Computer RAM.Must be clocked.Clock (>)DAction--No change1Q = 0Q = 1
120 Digital Logic Synchronous Logic T flip-flop Toggles state with each clock pulse.D flip-flop with Q output connected to D input.Clock (>)TAction--No change1Toggle (Q = not Q)
121 Digital Logic Synchronous Logic Shift Register Cascaded D flip-flops. Converts serial data to parallel data & vice versa.
122 Digital Logic Synchronous Logic Monostable multivibrator (One-shot) Generates one pulse with each trigger.Pulse length determined by R-C time constant.Astable multivibrator (Oscillator)Generates series of pulses.Pulse length & time between pulses determined by R-C time constants.
123 Digital Logic Synchronous Logic 555 Timer I.C. One of the most popular IC’s ever made.1 billion/year.Monostable or astable multivibrator.
124 Digital Logic Synchronous Logic 555 Monostable multivibrator T = 1.1 x R x C
125 Digital Logic Synchronous Logic 555 Astable multivibrator f = Ratio of R1 to R2 sets duty cycle.1.46C1 x (R1 + (2 x R2))
126 E7A01 -- Which of the following is a bistable circuit? An "AND" gateAn "OR" gateA flip-flopA clock
127 E7A02 -- How many output level changes are obtained for every two trigger pulses applied to the input of a T flip-flop circuit?NoneOneTwoFour
128 E7A03 -- Which of the following can divide the frequency of a pulse train by 2? An XOR gateA flip-flopAn OR gateA multiplexer
129 E7A04 -- How many flip-flops are required to divide a signal frequency by 4? 1248
130 Monostable multivibrator J-K flip-flop T flip-flop E7A05 -- Which of the following is a circuit that continuously alternates between two states without an external clock?Monostable multivibratorJ-K flip-flopT flip-flopAstable multivibrator
131 E7A06 -- What is a characteristic of a monostable multivibrator? It switches momentarily to the opposite binary state and then returns, after a set time, to its original stateIt is a clock that produces a continuous square wave oscillating between 1 and 0It stores one bit of data in either a 0 or 1 stateIt maintains a constant output voltage, regardless of variations in the input voltage
132 E7A13 -- What is an SR or RS flip-flop? A speed-reduced logic device with high power capabilityA set/reset flip-flop whose output is low when R is high and S is low, high when S is high and R is low, and unchanged when both inputs are lowA speed-reduced logic device with very low voltage operation capabilityA set/reset flip-flop that toggles whenever the T input is pulsed, unless both inputs are high
133 E7A14 -- What is a JK flip-flop? A flip-flop similar to an RS except that it toggles when both J and K are highA flip-flop utilizing low power, low temperature Joule-Kelvin devicesA flip-flop similar to a D flip-flop except that it triggers on the negative clock edgeA flip-flop originally developed in Japan and Korea which has very low power consumption
134 E7A15 -- What is a D flip-flop? A flip-flop whose output takes on the state of the D input when the clock signal transitions from low to highA differential class D amplifier used as a flip-flop circuitA dynamic memory storage elementA flip-flop whose output is capable of both positive and negative voltage excursions
135 Digital Logic Frequency Dividers and Counters Divide-by-N counter. A series of flip-flops connected so that one output pulse occurs after every N pulses.Each flip-flop divides by 2.Most counters provide an input to clear count.Counters can either count up or down.A decade counter divides by 10.A 4-stage counter (divide by 16) with feedback to reset after 10 input pulses.
136 Digital Logic Frequency Dividers and Counters Asynchronous (ripple) counter.Each input pulse triggers the following stage, so the count “ripples” along the chain.
137 Digital Logic Frequency Dividers and Counters Synchronous counter. Each stage in counter triggered by common clock, so each stage in counter changes state at the same time.
138 Digital Logic Frequency Dividers and Counters Frequency counters and references.A frequency counter is one of the most accurate means of determining a frequency.Counts number of pulses during a specified time interval & displays result.At VHF and higher frequencies, most counters use a “prescaler” to divide frequency by 10 or 100 before actual counting takes place.
139 Digital Logic Frequency Dividers and Counters Frequency counters and references.Frequency counter accuracy determined by a highly accurate reference oscillator called a “time base”.Temperature stable crystal oscillator.For extreme accuracy, an external reference can be used.GPS-disciplined oscillator.Rubidium reference oscillator.
140 Digital Logic Frequency Dividers and Counters Frequency counters and references.For counting low frequencies, reference oscillator & input signals are reversed.Time base oscillator is fed to input of counter.Input signal used as the time base.Measures period of signal & calculates frequency.
141 Digital Logic Frequency Dividers and Counters Marker generators. A high-stability crystal oscillator that generates a series of pulses at a known frequency.A frequency divider generates pulses at sub-multiples of reference frequency.
142 Digital Logic Frequency Dividers and Counters Marker generators. Selectable marker intervals.100 kHz, 50 kHz, 25 kHz.
143 E7F01 -- What is the purpose of a prescaler circuit? It converts the output of a JK flip flop to that of an RS flip-flopIt multiplies a higher frequency signal so a low-frequency counter can display the operating frequencyIt prevents oscillation in a low-frequency counter circuitIt divides a higher frequency signal so a low-frequency counter can display the input frequency
144 E7F02 -- Which of the following would be used to reduce a signal’s frequency by a factor of ten? A preampA prescalerA marker generatorA flip-flop
145 E7F03 -- What is the function of a decade counter digital IC? It produces one output pulse for every ten input pulsesIt decodes a decimal number for display on a seven-segment LED displayIt produces ten output pulses for every input pulseIt adds two decimal numbers together
146 E7F04 -- What additional circuitry must be added to a 100-kHz crystal-controlled marker generator so as to provide markers at 50 and 25 kHz?An emitter-followerTwo frequency multipliersTwo flip-flopsA voltage divider
147 E7F05 -- Which of the following is a technique for providing high stability oscillators needed for microwave transmission and reception?Use a GPS signal referenceUse a rubidium stabilized reference oscillatorUse a temperature-controlled high Q dielectric resonatorAll of these choices are correct
148 E7F06 -- What is one purpose of a marker generator? To add audio markers to an oscilloscopeTo provide a frequency reference for a phase locked loopTo provide a means of calibrating a receiver's frequency settingsTo add time signals to a transmitted signal
149 E7F07 -- What determines the accuracy of a frequency counter? The accuracy of the time baseThe speed of the logic devices usedAccuracy of the AC input frequency to the power supplyProper balancing of the mixer diodes
150 E7F08 -- Which of the following is performed by a frequency counter? Determining the frequency deviation with an FM discriminatorMixing the incoming signal with a WWV referenceCounting the number of input pulses occurring within a specific period of timeConverting the phase of the measured signal to a voltage which is proportional to the frequency
151 E7F09 -- What is the purpose of a frequency counter? To provide a digital representation of the frequency of a signalTo generate a series of reference signals at known frequency intervalsTo display all frequency components of a transmitted signalTo provide a signal source at a very accurate frequency
152 E7F10 -- What alternate method of determining frequency, other than by directly counting input pulses, is used by some counters?GPS averagingPeriod measurement plus mathematical computationPrescalingD/A conversion
153 E7F11 -- What is an advantage of a period-measuring frequency counter over a direct-count type? It can run on battery power for remote measurementsIt does not require an expensive high-precision time baseIt provides improved resolution of low-frequency signals within a comparable time periodIt can directly measure the modulation index of an FM transmitter
154 Digital Logic Logic Families Several different technologies can be used to build digital circuits.Vacuum tube.RTLECLTTLCMOSBiCMOSTri-State Logic
159 Digital Logic Logic Families Complementary Metal-Oxide Semiconductor (CMOS)3-18 VDC supply voltage.High level: Vdd – 0.1 V.Low level: Vss V.Threshold: ~ ½ supply voltage.High noise immunity.Sensitive to static damage.Low power consumption.Current pulse during switchover.
160 Digital Logic BiCMOS Logic High input impedance of CMOS.Static-sensitive.Low output impedance of bipolar.Higher power consumption.Complex manufacturing process.More expensive.BiCMOS LogicCombines Bipolar & CMOS devices on same chip.VoutVdd VinT2 T4 T1 T3 CL
161 E6A13 -- What do the initials CMOS stand for? Common Mode Oscillating SystemComplementary Mica-Oxide SiliconComplementary Metal-Oxide SemiconductorCommon Mode Organic Silicon
162 E6C01 -- What is the recommended power supply voltage for TTL series integrated circuits? 12 volts1.5 volts5 volts13.6 volts
163 E6C02 -- What logic state do the inputs of a TTL device assume if they are left open? A logic-high stateA logic-low stateThe device becomes randomized and will not provide consistent high or low-logic statesOpen inputs on a TTL device are ignored
164 E6C05 -- Which of the following is an advantage of CMOS logic devices over TTL devices? Differential output capabilityLower distortionImmune to damage from static dischargeLower power consumption
165 E6C06 -- Why do CMOS digital integrated circuits have high immunity to noise on the input signal or power supply?Larger bypass capacitors are used in CMOS circuit designThe input switching threshold is about two times the power supply voltageThe input switching threshold is about one-half the power supply voltageInput signals are stronger
166 E6C12 -- What is BiCMOS logic? A logic device with two CMOS circuits per packageAn FET logic family based on bimetallic semiconductorsA logic family based on bismuth CMOS devicesAn integrated circuit logic family using both bipolar and CMOS transistors
167 E6C13 -- Which of the following is an advantage of BiCMOS logic? Its simplicity results in much less expensive devices than standard CMOSIt is totally immune to electrostatic damageIt has the high input impedance of CMOS and the low output impedance of bipolar transistorsAll of these choices are correct
169 E6F01 -- What is photoconductivity? The conversion of photon energy to electromotive energyThe increased conductivity of an illuminated semiconductorThe conversion of electromotive energy to photon energyThe decreased conductivity of an illuminated semiconductor
170 E6F02 -- What happens to the conductivity of a photoconductive material when light shines on it? It increasesIt decreasesIt stays the sameIt becomes unstable
171 E6F06 -- Which of these materials is affected the most by photoconductivity? A crystalline semiconductorAn ordinary metalA heavy metalA liquid semiconductor
172 Optoelectronics Optoelectronic Components Phototransistor. A transistor in a clear package to allow light to hit the junction.Transistor turns on when exposed to light.External base connection may or may not be provided.
173 Optoelectronics Optoelectronic Components Optoisolator or optocoupler. LED & phototransistor in same packageVery high impedance between light source & phototransistor.High degree of isolation between control circuit & power circuit.
174 Optoelectronics Optoelectronic Components Optoisolator or optocoupler. Current transfer ratio (CTR)Ratio of output current to input current.Can use a darlington phototransistor to increase CTR.
175 Optoelectronics Optoelectronic Components Optical shaft encoder. Used for VFO knobs & other controls in many modern rigs.Using 2 detectors allows speed of rotation to be detected.
176 E6F03 -- What is the most common configuration of an optoisolator or optocoupler? A lens and a photomultiplierA frequency modulated helium-neon laserAn amplitude modulated helium-neon laserAn LED and a phototransistor
177 E6F05 -- Which of the following describes an optical shaft encoder? A device which detects rotation of a control by interrupting a light source with a patterned wheelA device which measures the strength a beam of light using analog to digital conversionA digital encryption device often used to encrypt spacecraft control signalsA device for generating RTTY signals by means of a rotating light source.
178 E6F07 -- What is a solid state relay? A relay using transistors to drive the relay coilA device that uses semiconductor devices to implement the functions of an electromechanical relayA mechanical relay that latches in the on or off state each time it is pulsedA passive delay line
179 E6F08 -- Why are optoisolators often used in conjunction with solid state circuits when switching 120 VAC?Optoisolators provide a low impedance link between a control circuit and a power circuitOptoisolators provide impedance matching between the control circuit and power circuitOptoisolators provide a very high degree of electrical isolation between a control circuit and the circuit being switchedOptoisolators eliminate the effects of reflected light in the control circuit
180 Optoelectronics Photovoltaic Cells. Photoelectric effect can be used in reverse to generate power.
181 Optoelectronics Photovoltaic Cells. If sufficient light falls on a P-N junction, free electrons in the N-type material will absorb energy & flow across the junction into the P-type material.Most common material is Silicon.Most efficient material is Gallium-Arsenide.Fully-illuminated junction yields about 0.5 VDC.Rapidly becoming commercially viable for power generation.
182 E6F04 -- What is the photovoltaic effect? The conversion of voltage to current when exposed to lightThe conversion of light to electrical energyThe conversion of electrical energy to mechanical energyThe tendency of a battery to discharge when used outside
183 E6F09 -- What is the efficiency of a photovoltaic cell? The output RF power divided by the input dc powerThe effective payback periodThe open-circuit voltage divided by the short-circuit current under full illuminationThe relative fraction of light that is converted to current
184 E6F10 -- What is the most common type of photovoltaic cell used for electrical power generation? SeleniumSiliconCadmium SulfideCopper oxide
185 E6F11 -- Which of the following is the approximate open-circuit voltage produced by a fully-illuminated silicon photovoltaic cell?0.1 V0.5 V1.5 V12 V
186 E6F12 -- What absorbs the energy from light falling on a photovoltaic cell? ProtonsPhotonsElectronsHoles