During voltage regulation, which diode is designed to operate in reverse breakdown?
A Schottky diode
B LED
C Varactor
D Zener diode
Answer: D. Zener diode A Zener diode is commonly operated in reverse breakdown to maintain an approximately stable voltage.
What bandgap property makes gallium arsenide useful for efficient light emission?
A Metallic bonding
B Indirect bandgap
C Zero bandgap
D Direct bandgap
Answer: D. Direct bandgap Gallium arsenide is a direct-bandgap semiconductor, which supports efficient radiative recombination.
At room temperature, silicon’s bandgap is closest to which value?
A 1.12 eV
B 0.20 eV
C 1.80 eV
D 0.66 eV
Answer: A. 1.12 eV Silicon’s bandgap at room temperature is about 1.12 eV.
Germanium’s room-temperature bandgap is approximately what?
A 1.42 eV
B 1.12 eV
C 2.20 eV
D 0.66 eV
Answer: D. 0.66 eV Germanium has a room-temperature bandgap of approximately 0.66 eV.
How many diodes form a standard full-wave bridge rectifier?
A Eight
B Four
C Six
D Two
Answer: B. Four A standard single-phase bridge rectifier uses four diodes.
Contacting a metal with a semiconductor forms what junction?
A MOS channel
B p–n junction
C Metal–semiconductor junction
D Bipolar junction
Answer: C. Metal–semiconductor junction A Schottky contact is a metal–semiconductor junction, often designed for rectifying behavior.
What chiefly controls current in a MOSFET?
A Emitter doping
B Collector voltage
C Gate electric field
D Base current
Answer: C. Gate electric field A MOSFET uses the gate electric field to control channel charge and drain current.
Name the three terminals of a bipolar junction transistor.
A Emitter, base, collector
B Anode, cathode, gate
C Gate, drain, source
D Source, body, gate
Answer: A. Emitter, base, collector A BJT has emitter, base, and collector terminals.
For an NPN transistor, which carriers dominate conduction through the emitter?
A Holes
B Electrons
C Photons
D Ions
Answer: B. Electrons Electrons are the majority carriers injected from the emitter of an NPN transistor.
Compared with the base, how is a BJT emitter usually doped?
A More heavily
B Only intrinsically
C Not doped
D Less heavily
Answer: A. More heavily The emitter is heavily doped to inject carriers efficiently into the base.
Amplification and switching are common functions of which device?
A Amplifying and switching
B Heating and cooling
C Filtering and sensing
D Rectifying and storing
Answer: A. Amplifying and switching Bipolar junction transistors are widely used as amplifiers and electronic switches.
At VGS = 0, what is the ideal state of an enhancement nMOS?
A In avalanche
B Strongly on
C In breakdown
D Off
Answer: D. Off An enhancement nMOS normally has no conducting inversion channel at zero gate-to-source voltage.
Negative gate voltage relative to source activates which enhancement device?
A More negative
B Exactly equal
C More positive
D Alternating rapidly
Answer: A. More negative A sufficiently negative gate-to-source voltage creates a hole channel in a p-channel enhancement MOSFET.
On a p-type MOS substrate, what forms after a sufficiently positive gate voltage is applied?
A Metallic depletion
B Electron inversion layer
C Avalanche region
D Hole accumulation only
Answer: B. Electron inversion layer A sufficiently positive gate voltage repels holes and attracts electrons, forming an inversion layer.
Variable reverse-bias capacitance identifies what diode?
A Schottky
B LED
C Zener
D Varactor
Answer: D. Varactor A varactor uses the voltage-dependent depletion capacitance of a reverse-biased junction.
Heavy doping and a negative-resistance region identify which diode?
A Solar cell
B Tunnel diode
C Phototransistor
D PIN diode
Answer: B. Tunnel diode Heavy doping makes the depletion region extremely thin, enabling tunneling and a negative-resistance region.
Intrinsic material between p and n regions defines what diode structure?
A Zener
B PIN diode
C Tunnel diode
D LED
Answer: B. PIN diode A PIN diode has p-type, intrinsic, and n-type regions in sequence.
What physical process drives avalanche breakdown in a reverse-biased junction?
A Carrier trapping
B Thermionic cooling
C Impact ionization
D Photon emission
Answer: C. Impact ionization High-field carriers create additional electron–hole pairs by impact ionization, causing avalanche multiplication.
After reverse breakdown begins, which quantity rises sharply if the circuit allows it?
A Forward voltage
B Bandgap energy
C Reverse current
D Doping density
Answer: C. Reverse current Breakdown creates a large reverse current; external resistance is needed to limit it.
Majority carriers dominate current transport in which diode?
A Minority carriers
B Ions
C Photons
D Majority carriers
Answer: D. Majority carriers Schottky conduction primarily involves majority carriers, so stored minority-carrier charge is small.
Relative to a p–n diode, what is a common Schottky-diode advantage?
A Higher forward drop
B Higher storage delay
C Faster switching
D No reverse leakage
Answer: C. Faster switching With little minority-carrier charge storage, Schottky diodes can switch rapidly.
In a common-emitter circuit, which BJT terminal is shared by input and output?
A gate
B emitter
C base
D collector
Answer: C. base Forward-active operation requires a forward-biased base–emitter junction and reverse-biased base–collector junction.
For an NPN transistor, which semiconductor type forms its base region?
A p-type
B n-type
C intrinsic
D metallic
Answer: A. p-type An NPN transistor has n-type emitter and collector regions separated by a p-type base.
What sets an ordinary rectifier diode’s maximum reverse voltage?
A Junction breakdown
B Thermal generation only
C Gate oxidation
D Optical absorption
Answer: A. Junction breakdown Reverse voltage is limited by the junction’s breakdown mechanisms and device design.
For a BJT, beta is defined as which current ratio?
A Emitter current to collector voltage
B Collector current to base current
C Base-to-emitter voltage
D Collector-to-base current ratio
Answer: B. Collector current to base current Common-emitter current gain beta is the ratio of collector current to base current.