101️⃣
Q: A diode in reverse bias is equivalent to
Options:
A) Open circuit
B) Short circuit
C) Low resistance path
D) None of these
Answer: A) Open circuit
Explanation:
In reverse bias, only a tiny leakage current flows, so practically it behaves as an open circuit.
102️⃣
Q: The reverse breakdown voltage of a Zener diode depends on
Options:
A) Doping level
B) Temperature
C) Junction area
D) All of the above
Answer: D) All of the above
Explanation:
Breakdown voltage varies with doping concentration, temperature, and physical dimensions of the junction.
103️⃣
Q: The forward current in a diode increases exponentially with
Options:
A) Reverse voltage
B) Forward voltage
C) Temperature
D) Frequency
Answer: B) Forward voltage
Explanation:
The diode current–voltage relation is , showing exponential increase with forward voltage.
104️⃣
Q: The typical reverse saturation current for a silicon diode is
Options:
A) 10 A
B) 1 mA
C) 1 μA
D) 1 nA
Answer: D) 1 nA
Explanation:
For silicon diodes, reverse saturation current is very small (nanometer range) due to fewer minority carriers.
105️⃣
Q: When temperature increases, reverse saturation current of a diode
Options:
A) Decreases
B) Remains constant
C) Increases exponentially
D) Becomes zero
Answer: C) Increases exponentially
Explanation:
Thermal energy creates more minority carriers, thus increasing reverse saturation current exponentially with temperature.
106️⃣
Q: The dynamic resistance of a diode is
Options:
A) Inverse of the slope of I–V curve
B) Equal to static resistance
C) Independent of bias
D) Always constant
Answer: A) Inverse of the slope of I–V curve
Explanation:
Dynamic (AC) resistance = dV/dI, i.e., the reciprocal of the slope of the I–V characteristic curve at the operating point.
107️⃣
Q: In a half-wave rectifier, the ripple factor is
Options:
A) 0.482
B) 1.21
C) 0.707
D) 2.21
Answer: B) 1.21
Explanation:
Ripple factor (γ) = for half-wave rectification.
108️⃣
Q: For a full-wave rectifier, the efficiency is
Options:
A) 40.6%
B) 50%
C) 81.2%
D) 100%
Answer: C) 81.2%
Explanation:
Maximum rectification efficiency of a full-wave rectifier = 81.2%.
109️⃣
Q: Peak Inverse Voltage (PIV) for a half-wave rectifier is
Options:
A) Vm
B) 2Vm
C) Vm/2
D) √2Vm
Answer: A) Vm
Explanation:
The diode must withstand the full peak secondary voltage in reverse bias — equal to Vm.
110️⃣
Q: Peak Inverse Voltage (PIV) for a full-wave rectifier (center-tap type) is
Options:
A) Vm
B) 2Vm
C) Vm/2
D) 3Vm
Answer: B) 2Vm
Explanation:
Each diode must withstand twice the peak secondary voltage when the other conducts in a center-tapped configuration.
111️⃣
Q: The main function of a capacitor filter in a rectifier circuit is
Options:
A) To step up voltage
B) To convert AC to DC
C) To reduce ripple
D) To stabilize input
Answer: C) To reduce ripple
Explanation:
A capacitor filter smooths out voltage variations by charging and discharging, thereby reducing ripple in rectified output.
112️⃣
Q: The reverse recovery time of a diode is
Options:
A) The time taken to turn ON
B) The time to remove stored charge
C) The total switching time
D) None
Answer: B) The time to remove stored charge
Explanation:
Reverse recovery time is the time needed for minority carriers to recombine and for the diode to block current after forward conduction.
113️⃣
Q: Which diode is used for high-frequency applications?
Options:
A) Tunnel diode
B) Varactor diode
C) Schottky diode
D) Zener diode
Answer: C) Schottky diode
Explanation:
Schottky diodes have very low forward voltage drop and fast switching, making them suitable for high-frequency circuits.
114️⃣
Q: Schottky diode is made by joining
Options:
A) P-type and N-type semiconductors
B) Metal and semiconductor
C) Two P-type materials
D) Two N-type materials
Answer: B) Metal and semiconductor
Explanation:
Schottky diodes form a metal–semiconductor junction instead of a P–N junction.
115️⃣
Q: The forward voltage drop of a Schottky diode is approximately
Options:
A) 0.1–0.3 V
B) 0.5–0.7 V
C) 1.0 V
D) 2.2 V
Answer: A) 0.1–0.3 V
Explanation:
Because it lacks a depletion layer, a Schottky diode’s forward voltage drop is much smaller than a silicon diode’s.
116️⃣
Q: Which diode is used as a variable capacitor?
Options:
A) Zener diode
B) Varactor diode
C) Tunnel diode
D) LED
Answer: B) Varactor diode
Explanation:
A varactor diode works in reverse bias; its capacitance varies with the applied voltage.
117️⃣
Q: The light emitted by an LED depends on
Options:
A) Doping concentration
B) Forward current
C) Bandgap energy of semiconductor
D) Both B and C
Answer: D) Both B and C
Explanation:
LED color (wavelength) depends on the bandgap, and intensity depends on forward current.
118️⃣
Q: The most suitable material for infrared LED is
Options:
A) GaAs
B) Si
C) Ge
D) GaP
Answer: A) GaAs
Explanation:
Gallium Arsenide (GaAs) emits infrared light efficiently.
119️⃣
Q: In photodiode operation, the current is proportional to
Options:
A) Bias voltage
B) Light intensity
C) Temperature
D) Junction area
Answer: B) Light intensity
Explanation:
Photodiodes generate current proportional to the incident light intensity when reverse biased.
120️⃣
Q: In Zener breakdown, the dominant mechanism is
Options:
A) Avalanche ionization
B) Quantum tunneling
C) Impact ionization
D) Recombination
Answer: B) Quantum tunneling
Explanation:
In heavily doped diodes (Zener region), breakdown occurs due to tunneling of electrons through a narrow depletion region
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