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WorksheetsElectron Devices and Circuits Quiz 1
Total questions: 20
Worksheet time: 7mins
In the energy band structure, what distinguishes a conductor from an insulator?
Conductors have no energy gap between valence and conduction bands
Insulators have a large energy gap (> 5 eV) between valence and conduction bands
Conductors have overlapping valence and conduction bands
All of the above
The energy gap of silicon at room temperature is approximately:
0.7 eV
1.1 eV
1.4 eV
3.2 eV
In an intrinsic semiconductor at room temperature, the carrier concentration is:
Equal number of electrons and holes
More electrons than holes
More holes than electrons
Zero carriers
When a trivalent impurity is added to pure silicon, it creates:
N-type semiconductor with excess electrons
P-type semiconductor with excess holes
Intrinsic semiconductor
Insulator
The minority carrier concentration in an N-type semiconductor:
Increases with temperature
Decreases with temperature
Remains constant
Becomes zero
In a PN junction diode under forward bias:
The depletion region width increases
The barrier potential increases
Current flows easily
The junction acts as an open circuit
The knee voltage of a silicon diode is approximately:
0.3 V
0.7 V
1.1 V
1.4 V
In a half-wave rectifier, the efficiency is approximately:
40.6%
81.2%
66.7%
90%
The ripple factor of a full-wave center-tap rectifier is:
1.21
0.482
0.693
0.406
Which rectifier circuit provides the highest efficiency?
Half-wave rectifier
Full-wave center-tap rectifier
Bridge rectifier
All have same efficiency
The main advantage of a bridge rectifier over a center-tap rectifier is:
Higher efficiency
Better transformer utilization factor
Lower ripple factor
Simpler circuit
A Zener diode is primarily used in:
Forward bias only
Reverse bias only
Both forward and reverse bias
As a switch
The Zener breakdown occurs due to:
Avalanche multiplication
High electric field
Thermal effects
Both a and b
For a Zener diode to act as a voltage regulator, it must operate in:
Forward bias region
Reverse bias region beyond breakdown
Cutoff region
Saturation region
When temperature increases in a PN junction diode, which of the following phenomena occurs and why?
Forward voltage increases because carrier mobility decreases
Forward voltage decreases because intrinsic carrier concentration increases exponentially
Reverse saturation current decreases because fewer carriers are available
The depletion width increases because thermal energy creates more fixed charges
Which material is commonly used for red LEDs?
Gallium Arsenide (GaAs)
Gallium Arsenide Phosphide (GaAsP)
Gallium Phosphide (GaP)
Silicon (Si)
LCD stands for:
Light Collecting Diode
Liquid Crystal Display
Light Conducting Display
Laser Crystal Display
Why does the reverse saturation current in a PN junction diode increase exponentially with temperature, and what are the implications for circuit design?
Thermal energy breaks more covalent bonds creating electron-hole pairs; requires temperature compensation in precision circuits
Higher temperature increases carrier mobility; necessitates current limiting resistors
Increased thermal vibration reduces barrier height; improves switching speed at high temperatures
Temperature causes lattice expansion reducing carrier concentration; requires thermal isolation
In a full-wave rectifier, why is the ripple factor lower than in a half-wave rectifier, and what is the theoretical limit of ripple reduction?
Lower ripple because both half-cycles are used; theoretical limit is zero with infinite capacitance
Lower ripple due to transformer center-tap; limit is determined by diode voltage drop
Ripple is lower because of higher frequency; limit is set by transformer losses
Both cycles contribute to smoothing; limit depends on load resistance value
Why does a Zener diode maintain constant voltage in the breakdown region, and what would happen if the series resistance is too small?
Constant voltage is due to avalanche multiplication; small resistance causes thermal runaway
Constant voltage is due to depletion capacitance; small resistance reduces regulation
The voltage is constant because of tunneling effect; small resistance improves regulation
Voltage regulation occurs due to negative temperature coefficient; small resistance has no effect
