Learn/ Extra course/Module 4 of 10
Extra Course, Module 4: Semiconductors and the Deep Parts Bin
Covers NCVEC 2024-2028 Extra Pool, Subelement E6 (Circuit Components). Six questions on your exam come from this material.
Ray sets a single silicon diode on the bench next to a sliver of circuit board dense with parts smaller than rice. "Same physics in both," he says. "Extra components is where we finally open the crystal itself: what the electrons and holes are doing, why each diode family exists, how logic thinks, what ferrite actually is, why microwave parts look the way they do, and how light became a circuit element. Six drawers. Deep ones."
4.1Inside the Crystal
Semiconductor physics in four moves:
- Doping creates the personalities. N-type material contains excess free electrons (donor impurities gave them). An acceptor impurity adds holes instead, creating P-type. Current is electrons and holes trading places, and every semiconductor device is an arrangement of N against P.
- The junction. Reverse-bias a PN diode and it does not conduct because the applied voltage pulls holes and electrons apart, widening the depletion region, an insulating no-man's-land at the junction. Forward bias collapses it, and a silicon NPN transistor shows it is biased on by a base-to-emitter voltage of approximately 0.6 to 0.7 volts, the silicon threshold from the General course now doing diagnostic duty: probe Vbe, read the truth.
- The bipolar transistor, specified. Its beta is the change in collector current with respect to the change in base current, the current gain as a ratio of changes. Its speed limit has a name: the alpha cutoff frequency, where grounded-base current gain falls to 0.7 of its 1 kHz value.
- The FET family. A FET's gate presents much higher DC input impedance than a bipolar transistor's base, the insulated-gate construction from the General course paying off as near-zero input current. A depletion-mode FET conducts between source and drain with no gate voltage applied; you bias it to reduce current, the opposite of the enhancement-mode parts in your radio's finals. And the static-electricity vulnerability from General gets its cure: Zener diodes connected between a MOSFET's gate and its source or drain protect the gate from static damage, sacrificial clamps built into nearly every modern MOSFET.
Materials matter at the extremes: gallium arsenide serves in microwave circuits, where silicon runs out of speed. Hold that thought for Section 4.5.
Website note: this page will include the E6-1 symbol figure (FET variants) redrawn with labeled and quiz versions.
Quiz yourself: identify the transistors by number
Knowledge Check 4.1
Tap an answer. In your own words first, then check yourself.
1. What does reverse bias do to a PN junction?
2. What is a transistor's beta?
3. Why are Zener diodes built between a MOSFET's gate and source?
E6A the easy way: all 12 questions, with the right answer
Every pool question in this group. Read the answer, let the tip make it stick.
E6A01 In what application is gallium arsenide used as a semiconductor material?
Answer In microwave circuits
Tip Gallium arsenide moves electrons fast, so it shines in microwave circuits where silicon runs out of speed.
E6A02 Which of the following semiconductor materials contains excess free electrons?
Answer N-type
Tip N is for negative, and the negative carriers are the extra free electrons, so N-type has them to spare.
E6A03 Why does a PN-junction diode not conduct current when reverse biased?
Answer Holes in P-type material and electrons in the N-type material are separated by the applied voltage, widening the depletion region
Tip Reverse bias pulls holes and electrons away from the junction, so the depletion region grows wide and blocks current.
E6A04 What is the name given to an impurity atom that adds holes to a semiconductor crystal structure?
Answer Acceptor impurity
Tip An acceptor atom is short an electron, so it accepts one and leaves a hole behind.
E6A05 How does DC input impedance at the gate of a field-effect transistor (FET) compare with that of a bipolar transistor?
Answer An FET has higher input impedance
Tip An FET gate is a tiny capacitor, not a forward junction, so its DC input impedance towers over a bipolar's.
E6A06 What is the beta of a bipolar junction transistor?
Answer The change in collector current with respect to the change in base current
Tip Beta is current gain, the collector current change divided by the base current change that drove it.
E6A07 Which of the following indicates that a silicon NPN junction transistor is biased on?
Answer Base-to-emitter voltage of approximately 0.6 volts to 0.7 volts
Tip A silicon junction turns on near 0.6 to 0.7 volts, so that base-emitter reading means the NPN is conducting.
E6A08 What is the term for the frequency at which the grounded-base current gain of a bipolar junction transistor has decreased to 0.7 of the gain obtainable at 1 kHz?
Answer Alpha cutoff frequency
Tip Alpha cutoff is where grounded-base gain sags to 0.7 of its low frequency value, the transistor's high end.
E6A09 What is a depletion-mode field-effect transistor (FET)?
Answer An FET that exhibits a current flow between source and drain when no gate voltage is applied
Tip Depletion mode is normally on, so source to drain conducts even with zero gate voltage, and the gate pinches it off.
E6A10 In Figure E6-1, which is the schematic symbol for an N-channel dual-gate MOSFET?
Answer 4
Tip A dual-gate N-channel MOSFET shows two gate leads, so symbol 4 is the one with the extra gate.
E6A11 In Figure E6-1, which is the schematic symbol for a P-channel junction FET?
Answer 1
Tip Symbol 1 is the P-channel JFET. For P-channel the gate arrow points outward, away from the channel.
E6A12 What is the purpose of connecting Zener diodes between a MOSFET gate and its source or drain?
Answer To protect the gate from static damage
Tip Those Zeners clamp stray static before it punches through the thin gate oxide, so they guard the gate from static damage.
4.2The Diode Family Reunion
At Technician a diode was a one-way valve. At Extra, it is a family where each member evolved for one job:
- Zener: maintains a constant voltage drop under varying current, run deliberately in reverse breakdown as a voltage reference. The regulator circuits of Module 5 stand on it.
- Schottky: a metal-semiconductor junction (no P material at all), prized for its lower forward voltage drop than silicon, which makes it the better power-supply rectifier (less voltage lost means less heat), and its speed makes it the standard VHF/UHF mixer and detector diode.
- Varactor: a diode designed as a voltage-controlled capacitor, the reverse-biased depletion region (Section 4.1's widening no-man's-land) used as a variable-plate spacing. Every synthesized VFO tunes with one.
- PIN: an intrinsic layer between P and N gives it low junction capacitance, making it the solid-state RF switch, and as a variable attenuator its attenuation is controlled by its forward DC bias current. Your transceiver's T/R switching is PIN diodes doing relay work with no moving parts.
- Point-contact: the antique that survives as an RF detector, a whisker on a crystal, literally the crystal set's crystal.
- LED: its forward voltage drop is determined by the semiconductor's band gap, which is also why color and voltage travel together: red LEDs drop less than blue because their photons carry less energy. The Technician "varies by type" answer, explained at last.
One failure mode covers them all: a junction diode subjected to excessive current fails from excessive junction temperature. Diodes do not die of amperes; they die of the heat amperes make.
Website note: E6-2 (diode symbols) gets the same labeled/quiz treatment.
Quiz yourself: identify the diodes by number
Knowledge Check 4.2
Tap an answer. In your own words first, then check yourself.
1. Why is a Schottky diode the better power supply rectifier?
2. Which diode is a voltage-controlled capacitor?
3. What actually destroys a diode carrying excessive current?
E6B the easy way: all 11 questions, with the right answer
Every pool question in this group. Read the answer, let the tip make it stick.
E6B01 What is the most useful characteristic of a Zener diode?
Answer A constant voltage drop under conditions of varying current
Tip A Zener holds its voltage steady while current swings, which is exactly what you want for a reference or regulator.
E6B02 Which characteristic of a Schottky diode makes it a better choice than a silicon junction diode for use as a power supply rectifier?
Answer Lower forward voltage drop
Tip A Schottky drops only about 0.3 volts versus silicon's 0.7, so less forward drop means less loss rectifying power.
E6B03 What property of an LED's semiconductor material determines its forward voltage drop?
Answer Band gap
Tip An LED's color and its forward voltage both trace back to the semiconductor band gap, bigger gap, higher voltage.
E6B04 What type of semiconductor device is designed for use as a voltage-controlled capacitor?
Answer Varactor diode
Tip A varactor is a tuning capacitor you steer with voltage, so more reverse bias means less capacitance.
E6B05 What characteristic of a PIN diode makes it useful as an RF switch?
Answer Low junction capacitance
Tip A PIN diode has very low junction capacitance, so at RF it can act like a clean switch instead of leaking signal across.
E6B06 Which of the following is a common use of a Schottky diode?
Answer As a VHF/UHF mixer or detector
Tip A Schottky switches fast and has low drop, making it a natural VHF and UHF mixer or detector.
E6B07 What causes a junction diode to fail from excessive current?
Answer Excessive junction temperature
Tip Too much current cooks the junction, so diodes die from excessive junction temperature, not voltage alone.
E6B08 Which of the following is a Schottky barrier diode?
Answer Metal-semiconductor junction
Tip Schottky means a metal to semiconductor junction, no P-N pair, which is why it switches so quickly.
E6B09 What is a common use for point-contact diodes?
Answer As an RF detector
Tip A point-contact diode has tiny capacitance and works up high, so it serves as an RF detector.
E6B10 In Figure E6-2, which is the schematic symbol for a Schottky diode?
Answer 6
Tip Symbol 6 is the Schottky diode. Look for the little S-shaped flag on the cathode bar.
E6B11 What is used to control the attenuation of RF signals by a PIN diode?
Answer Forward DC bias current
Tip You vary a PIN diode's RF attenuation by its forward DC bias current, more current means less resistance.
4.3How Logic Thinks
The digital drawer, from families to fragments:
Families. CMOS keeps its General-course crown for lowest power consumption, and gains an explanation for its famous noise immunity: its input switching threshold sits at about half the supply voltage, the widest possible margin from both rails. BiCMOS hybridizes: the high input impedance of CMOS with the low output impedance of bipolar transistors, each technology contributing its best terminal.
Building blocks:
- A comparator changes its output state when the input crosses the threshold voltage, and hysteresis (two thresholds, one for each direction) exists to prevent input noise from causing unstable output signals. Without it, a slowly drifting input chatters the output; with it, the decision sticks.
- Tri-state logic outputs offer 0, 1, and high impedance, the third state letting many devices share one bus by electrically stepping aside.
- A pull-up or pull-down resistor connects to the positive or negative supply to establish a voltage when an input or output would otherwise float. Floating inputs are noise antennas; the resistor gives them an opinion.
- Gate symbols (Figure E6-3): NAND, NOR, and the NOT inverter, the AND/OR shapes from your General course wearing the inversion bubble.
The programmable frontier: a field-programmable gate array (FPGA) is configured using a hardware description language (HDL). You do not wire an FPGA; you describe the circuit in text and the chip becomes it, which is how one part on an SDR board can be a filter today and a modem tomorrow.
Website note: E6-3 (logic symbols) joins the figure package.
Quiz yourself: identify the gates by number
Knowledge Check 4.3
Tap an answer. In your own words first, then check yourself.
1. Why does a comparator include hysteresis?
2. What are the three states of tri-state logic?
3. How is an FPGA's configuration designed?
E6C the easy way: all 11 questions, with the right answer
Every pool question in this group. Read the answer, let the tip make it stick.
E6C01 What is the function of hysteresis in a comparator?
Answer To prevent input noise from causing unstable output signals
Tip Hysteresis sets two thresholds, so a noisy input cannot rattle the output back and forth, it needs a real swing.
E6C02 What happens when the level of a comparator’s input signal crosses the threshold voltage?
Answer The comparator changes its output state
Tip A comparator is a decision maker, so when the input crosses the threshold it flips its output state.
E6C03 What is tri-state logic?
Answer Logic devices with 0, 1, and high-impedance output states
Tip Tri-state adds a high-impedance third state to 0 and 1, so a device can quietly let go of a shared bus.
E6C04 Which of the following is an advantage of BiCMOS logic?
Answer It has the high input impedance of CMOS and the low output impedance of bipolar transistors
Tip BiCMOS marries CMOS high input impedance to bipolar low output impedance, the best of both families.
E6C05 Which of the following digital logic families has the lowest power consumption?
Answer CMOS
Tip CMOS draws current mainly while switching, so at rest it sips almost nothing, lowest power of the families.
E6C06 Why do CMOS digital integrated circuits have high immunity to noise on the input signal or power supply?
Answer The input switching threshold is about half the power supply voltage
Tip CMOS decides at about half the supply, so noise has to climb halfway up before it fools the input.
E6C07 What best describes a pull-up or pull-down resistor?
Answer A resistor connected to the positive or negative supply used to establish a voltage when an input or output is an open circuit
Tip A pull-up or pull-down ties a floating line to a known rail, so an open input or output still reads a definite level.
E6C08 In Figure E6-3, which is the schematic symbol for a NAND gate?
Answer 2
Tip Symbol 2 is the NAND gate, an AND shape with the little inversion bubble on its output.
E6C09 What is used to design the configuration of a field-programmable gate array (FPGA)?
Answer Hardware description language (HDL)
Tip You describe an FPGA's logic in a hardware description language like VHDL or Verilog, then it configures itself.
E6C10 In Figure E6-3, which is the schematic symbol for a NOR gate?
Answer 4
Tip Symbol 4 is the NOR gate, an OR shape with the inversion bubble added at the output.
E6C11 In Figure E6-3, which is the schematic symbol for the NOT operation (inversion)?
Answer 5
Tip Symbol 5 is the NOT, the inverter, a triangle with a bubble that simply flips its single input.
4.4Iron, Ferrite, and the Singing Crystal
The magnetic drawer, with its physics finally attached:
- The core property that determines an inductor's inductance is the material's permeability, its appetite for magnetic flux. Insert brass into a coil and inductance decreases, the diamagnetic tuning slug running the effect backward.
- Push too much flux and the core saturates: inductor saturation is caused by operation at excessive magnetic flux, the core's appetite exceeded, inductance collapsing, distortion blooming.
- Ferrite versus powdered iron, the choice on every toroid order form: ferrite's high permeability means fewer turns for a given inductance; powdered iron's virtue is the highest temperature stability of its magnetic characteristics. Winding economy versus drift, chosen per job.
- Solid iron cores waste power in eddy currents, so transformer cores are built of thin laminated layers to interrupt them. The toroid's advantage repeats from the General course: it confines the magnetic field within the core.
- Ferrite's small-parts career continues: ferrite beads serve as VHF and UHF parasitic suppressors at the terminals of HF amplifier transistors, absorbing the frequencies where the amplifier would rather oscillate. Module 5's parasitic suppression, purchased for pennies.
Then the drawer's oddest resident: piezoelectricity, the characteristic of materials that generate a voltage when stressed and flex when a voltage is applied. Squeeze it, get volts; apply volts, it moves. A quartz crystal is a piezoelectric slab whose mechanical resonance is electrically accessible, and its equivalent circuit is a series RLC in parallel with a shunt capacitance (the electrodes and stray). That equivalent circuit has a spectacular property: the effective Q reaches values no wound inductor approaches, which is why crystals discipline every frequency standard you own, from the DDS reference of your transceiver to the wristwatch timing your FT8 slots.
Knowledge Check 4.4
Tap an answer. In your own words first, then check yourself.
1. Which core material property sets an inductor's inductance?
2. What causes inductor core saturation?
3. What is the equivalent circuit of a quartz crystal?
E6D the easy way: all 11 questions, with the right answer
Every pool question in this group. Read the answer, let the tip make it stick.
E6D01 What is piezoelectricity?
Answer A characteristic of materials that generate a voltage when stressed and that flex when a voltage is applied
Tip Piezoelectric material trades voltage and squeeze both ways, it makes voltage when stressed and flexes when driven.
E6D02 What is the equivalent circuit of a quartz crystal?
Answer Series RLC in parallel with a shunt C representing electrode and stray capacitance
Tip Model a crystal as a series RLC for its mechanical resonance, with a shunt C for the electrodes and stray capacitance.
E6D03 Which of the following is an aspect of the piezoelectric effect?
Answer Mechanical deformation of material due to the application of a voltage
Tip One side of the piezoelectric coin is this, apply a voltage and the material physically deforms.
E6D04 Why are cores of inductors and transformers sometimes constructed of thin layers?
Answer To reduce power loss from eddy currents in the core
Tip Laminating the core into thin layers breaks up circulating eddy currents, so it cuts that core power loss.
E6D05 How do ferrite and powdered iron compare for use in an inductor core?
Answer Ferrite cores generally require fewer turns to produce a given inductance value
Tip Ferrite has higher permeability than powdered iron, so it reaches a given inductance with fewer turns.
E6D06 What core material property determines the inductance of an inductor?
Answer Permeability
Tip Inductance rides on core permeability, how readily the core carries magnetic flux.
E6D08 Which of the following materials has the highest temperature stability of its magnetic characteristics?
Answer Powdered iron
Tip Powdered iron holds its magnetic traits steadiest with temperature, so it wins on temperature stability.
E6D09 What devices are commonly used as VHF and UHF parasitic suppressors at the input and output terminals of a transistor HF amplifier?
Answer Ferrite beads
Tip Slip ferrite beads on the leads to tame VHF and UHF parasitics on an HF transistor amplifier.
E6D10 What is a primary advantage of using a toroidal core instead of a solenoidal core in an inductor?
Answer Toroidal cores confine most of the magnetic field within the core material
Tip A toroid wraps the flux around inside its ring, so it keeps most of the magnetic field in the core and stays self-shielding.
E6D11 Which type of core material decreases inductance when inserted into a coil?
Answer Brass
Tip Brass is nonmagnetic, so sliding a brass slug in actually lowers inductance instead of raising it.
E6D12 What causes inductor saturation?
Answer Operation at excessive magnetic flux
Tip Push too much flux and the core saturates, it just cannot hold more, so inductance collapses.
4.5Built for Gigahertz
RF construction is a fight against Module 3's parasitics, and this drawer holds the weapons.
Materials first. Gallium arsenide earns its microwave role through higher electron mobility: its electrons simply move faster than silicon's. For MMICs pushing higher still, gallium nitride supports the highest frequencies. The exotic crystals exist because speed is a material property.
The MMIC, characterized. The General course named it; the Extra pool specifies it: MMICs offer controlled gain, low noise figure, and constant input and output impedance across their specified frequency range. All of that, in a part costing a few dollars. The supporting numbers: the standard MMIC input and output impedance is 50 ohms (matched to everything by design), a typical low-noise UHF preamplifier noise figure is around 0.5 dB, connections are made with microstrip transmission line etched on the board, and DC power arrives through a resistor and/or RF choke connected to the output lead, riding in on the same pin the RF leaves by.
Packaging is electrical design. The DIP (dual in-line package, two rows of pins on opposite sides) is the classic through-hole part, and it is banished from UHF work for one reason: excessive lead length, every pin a Module 3 parasitic inductor. The cure is surface-mount technology, whose RF advantages stack: smaller circuit area, shorter traces, and less parasitic inductance and capacitance per component. All of these. The rice-grain parts on Ray's board sliver are not miniaturization for its own sake; they are parasitics starved to death.
Knowledge Check 4.5
Tap an answer. In your own words first, then check yourself.
1. Why is gallium arsenide used above UHF?
2. What is the standard input and output impedance of MMICs?
3. Why are DIP packages avoided at UHF?
E6E the easy way: all 12 questions, with the right answer
Every pool question in this group. Read the answer, let the tip make it stick.
E6E01 Why is gallium arsenide (GaAs) useful for semiconductor devices operating at UHF and higher frequencies?
Answer Higher electron mobility
Tip GaAs electrons scoot faster than silicon's, so that higher mobility lets it work at UHF and above.
E6E02 Which of the following device packages is a through-hole type?
Answer DIP
Tip A DIP has leads that poke through holes in the board, so it is the through-hole part here.
E6E03 Which of the following materials supports the highest frequency of operation when used in MMICs?
Answer Gallium nitride
Tip Gallium nitride is the wide band gap champ, so it runs MMICs to the highest frequencies.
E6E04 Which is the most common input and output impedance of MMICs?
Answer 50 ohms
Tip MMICs are built for a 50 ohm world, so their input and output impedance is 50 ohms to match everything else.
E6E05 Which of the following noise figure values is typical of a low-noise UHF preamplifier?
Answer 0.5 dB
Tip A good low-noise UHF preamp posts well under a dB, so 0.5 dB is a typical noise figure.
E6E06 What characteristics of MMICs make them a popular choice for VHF through microwave circuits?
Answer Controlled gain, low noise figure, and constant input and output impedance over the specified frequency range
Tip MMICs give you a known gain, a low noise figure, and steady 50 ohm ports across the band, so they drop right in.
E6E07 What type of transmission line is often used for connections to MMICs?
Answer Microstrip
Tip MMICs usually connect through microstrip, a controlled-impedance trace printed right on the board.
E6E08 How is power supplied to the most common type of MMIC?
Answer Through a resistor and/or RF choke connected to the amplifier output lead
Tip The common MMIC feeds DC in on the same output lead, through a resistor and/or RF choke that blocks the signal.
E6E09 Which of the following component package types have the least parasitic effects at frequencies above the HF range?
Answer Surface mount
Tip Surface-mount parts have almost no leads, so above HF they carry the least parasitic stray L and C.
E6E10 What advantage does surface-mount technology offer at RF compared to using through-hole components?
Answer All these choices are correct
Tip SMT trims lead length and board size and improves high frequency behavior, so all those RF advantages apply.
E6E11 What is a characteristic of DIP packaging used for integrated circuits?
Answer Two rows of connecting pins on opposite sides of package (dual in-line package)
Tip DIP means dual in-line package, two rows of pins running down opposite sides of the body.
E6E12 Why are DIP through-hole package ICs not typically used at UHF and higher frequencies?
Answer Excessive lead length
Tip DIP leads are just too long for UHF, that extra lead length adds stray inductance that ruins the signal.
4.6Light as a Circuit Element
The last drawer converts between photons and electrons, both directions.
Light in, electricity out:
- In a photovoltaic cell, photons are absorbed, and the photovoltaic effect is the conversion of light to electrical energy. The engineering sheet: the most common material is silicon, a fully illuminated cell produces about 0.5 volts open-circuit (the same number your General solar section used), and a cell's efficiency is the relative fraction of light converted to current.
- Photoconductive material takes the passive route: shine light on it and its resistance decreases. The common photoconductive devices are made of crystalline semiconductor, and every light-activated sensor descends from this effect.
Light as a messenger:
- An optoisolator (optocoupler) is most commonly an LED and a phototransistor facing each other across a gap. Its purpose in circuits controlling 120 VAC: providing electrical isolation between the control circuit and the circuit being switched. Nothing crosses the gap but photons, so a fault on the mains side cannot reach the microcontroller. The solid-state relay packages this into a drop-in replacement: semiconductors implementing the functions of an electromechanical relay, no coil, no contacts, no arc.
- An optical shaft encoder detects rotation by interrupting a light source with a patterned wheel, and it is the part under your transceiver's VFO knob. The big knob has not touched a variable capacitor in decades; it has been chopping light beams and reporting the count to the DDS, which is as fitting a place as any to end the components course: even the tuning knob is optoelectronics now.
Knowledge Check 4.6
Tap an answer. In your own words first, then check yourself.
1. What happens to photoconductive material in light?
2. Why pair an optoisolator with circuits switching 120 VAC?
3. How does an optical shaft encoder sense rotation?
E6F the easy way: all 11 questions, with the right answer
Every pool question in this group. Read the answer, let the tip make it stick.
E6F01 What absorbs the energy from light falling on a photovoltaic cell?
Answer Electrons
Tip Light hands its energy to electrons in the cell, knocking them loose to carry current.
E6F02 What happens to photoconductive material when light shines on it?
Answer Resistance decreases
Tip Shine light on photoconductive material and it frees carriers, so its resistance drops.
E6F03 What is the most common configuration of an optoisolator or optocoupler?
Answer An LED and a phototransistor
Tip The usual optoisolator pairs an LED talking by light to a phototransistor listening, no wire between them.
E6F04 What is the photovoltaic effect?
Answer The conversion of light to electrical energy
Tip The photovoltaic effect is light going straight to electricity, which is how a solar cell works.
E6F05 Which of the following describes an optical shaft encoder?
Answer A device that detects rotation by interrupting a light source with a patterned wheel
Tip An optical shaft encoder chops a light beam with a slotted wheel, so the pulses tell you it is turning.
E6F06 Which of these materials is most commonly used to create photoconductive devices?
Answer Crystalline semiconductor
Tip Photoconductive devices lean on crystalline semiconductor, where incoming light frees charge carriers.
E6F07 What is a solid-state relay?
Answer A device that uses semiconductors to implement the functions of an electromechanical relay
Tip A solid-state relay does a mechanical relay's job with semiconductors, switching with no moving contacts.
E6F08 Why are optoisolators often used in conjunction with solid-state circuits that control 120 VAC circuits?
Answer Optoisolators provide an electrical isolation between a control circuit and the circuit being switched
Tip The optoisolator's light gap keeps the low-voltage control side electrically isolated from the 120 VAC side.
E6F09 What is the efficiency of a photovoltaic cell?
Answer The relative fraction of light that is converted to current
Tip Cell efficiency is just the fraction of incoming light it turns into usable current.
E6F10 What is the most common material used in power-generating photovoltaic cells?
Answer Silicon
Tip Silicon is cheap, abundant, and well understood, so it is the usual material for power solar cells.
E6F11 What is the approximate open-circuit voltage produced by a fully illuminated silicon photovoltaic cell?
Answer 0.5 volts
Tip One lit silicon cell sits around 0.5 volts open circuit, which is why panels stack many in series.
Review: every Exam Anchor from this module
E6A N-type: excess free electrons; acceptor impurity: adds holes. Reverse bias: widens the depletion region, blocking conduction. NPN biased on: Vbe about 0.6 to 0.7 V. Beta: change in collector current over change in base current. Alpha cutoff frequency: grounded-base gain down to 0.7 of the 1 kHz value. FET gate: higher DC input impedance than bipolar. Depletion-mode FET: conducts with zero gate voltage. Gate-protection Zeners: guard against static. Gallium arsenide: microwave circuits.
E6B Zener: constant voltage under varying current. Schottky: metal-semiconductor junction, lower forward drop, best rectifier choice, VHF/UHF mixer/detector. Varactor: voltage-controlled capacitor. PIN: low junction capacitance, RF switch; attenuation set by forward DC bias current. Point-contact: RF detector. LED forward drop: set by band gap. Overcurrent kills diodes via excessive junction temperature.
E6C CMOS: lowest power; noise immunity from a switching threshold near half the supply. BiCMOS: CMOS input impedance plus bipolar output impedance. Comparator: output changes at the threshold; hysteresis prevents noise-induced instability. Tri-state: 0, 1, high impedance. Pull-up/pull-down resistor: establishes a voltage on an otherwise open input or output. FPGA: designed with a hardware description language. Figure E6-3: NAND, NOR, NOT symbols.
E6D Permeability determines inductance; brass inserted in a coil decreases it. Saturation: excessive magnetic flux. Ferrite: fewer turns needed; powdered iron: best temperature stability. Laminated cores: reduce eddy current loss. Toroids confine the field. Ferrite beads: VHF/UHF parasitic suppressors on HF amplifier transistors. Piezoelectricity: voltage from stress, flexing from voltage. Quartz crystal equivalent: series RLC paralleled by shunt capacitance.
E6E GaAs: higher electron mobility for UHF and up; GaN: highest-frequency MMICs. MMICs: controlled gain, low noise figure, constant impedances (all); 50-ohm input and output; about 0.5 dB NF for a low-noise UHF preamp; microstrip interconnect; power via resistor/RF choke on the output lead. DIP: through-hole, dual in-line pins; unusable at UHF from excessive lead length. Surface mount: smaller area, shorter traces, lower parasitics (all).
E6F Photovoltaic: photons absorbed; light converted to electrical energy; silicon; about 0.5 V open-circuit; efficiency is the fraction of light converted. Photoconductive material: resistance decreases in light; made of crystalline semiconductor. Optoisolator: LED plus phototransistor; provides electrical isolation for AC control. Solid-state relay: semiconductor implementation of a relay. Optical shaft encoder: patterned wheel interrupting a light source.
Before you move on
Six drawers, fully opened: the crystal's physics, a diode for every job, logic with its families and fragments, magnetics with permeability attached, gigahertz construction, and light wired into the circuit. The habit this module installs is the Extra version of the General course's "which one and why": you now pick parts by mechanism.
Module 5 is the course's biggest: eight exam questions of practical circuits, assembling these parts into amplifiers, filters, power supplies, modulators, op-amps, oscillators, and the software-defined signal chain.
© 2026 Anthony Pelfanio, K4DIA. All rights reserved.