20+ Top p-n Junctions MCQ with Answers
What type of semiconductor junction is formed between a p-type semiconductor and an n-type semiconductor?
a) P-N junction
b) N-P junction
c) P-P junction
d) N-N junction
Answer: a
Hint: The junction is formed by the contact between p-type and n-type materials.
In a forward-biased p-n junction, the majority of carriers in the p-region are:
a) Electrons
b) Holes
c) Protons
d) Neutrons
Answer: b
Hint: In forward bias, holes move towards the n-region.
The depletion region in a p-n junction diode is:
a) Rich in free electrons
b) Rich in positive ions
c) Devoid of charge carriers
d) Devoid of impurities
Answer: c
Hint: The depletion region lacks mobile charge carriers.
When a reverse bias is applied to a p-n junction diode, the width of the depletion region:
a) Increases
b) Decreases
c) Remains the same
d) Becomes infinite
Answer: a
Hint: Reverse biasing widens the depletion region.
What is the voltage required to overcome the barrier potential in a forward-biased p-n junction?
a) Barrier voltage
b) Breakdown voltage
c) Saturation voltage
d) Turn-on voltage
Answer: d
Hint: The voltage that allows current flow in the forward direction is called the turn-on voltage.
In a reverse-biased p-n junction, the majority of carriers in the depletion region are:
a) Electrons
b) Holes
c) Protons
d) Neutrons
Answer: c
Hint: The depletion region has immobile positive ions.
The potential barrier in a p-n junction diode is caused by:
a) Majority carriers
b) Minority carriers
c) Impurity atoms
d) Electric field
Answer: d
Hint: The electric field at the junction causes the potential barrier.
The breakdown of a p-n junction due to a high reverse voltage is called:
a) Forward breakdown
b) Reverse breakdown
c) Zener breakdown
d) Avalanche breakdown
Answer: d
Hint: Avalanche breakdown occurs due to collision ionization.
What type of relationship does a diode exhibit in its current-voltage characteristics?
a) Linear
b) Quadratic
c) Exponential
d) Inverse
Answer: c) Exponential
Hint: Diodes follow an exponential relationship between current and voltage due to the physics of charge carriers crossing the depletion region.
In a resistor’s current-voltage characteristics, how does the current vary with voltage?
a) Linearly increases with voltage
b) Quadratically increases with voltage
c) Exponentially increases with voltage
d) Remains constant
Answer: a) Linearly increases with voltage
Hint: Resistors exhibit a linear relationship between current and voltage, according to Ohm’s law (I = V/R).
What is the current-voltage characteristic of an ideal voltage source?
a) Vertical line
b) Horizontal line
c) Diagonal line
d) Curved line
Answer: b) Horizontal line
Hint: An ideal voltage source maintains a constant voltage across its terminals, resulting in a horizontal line in its current-voltage graph.
What type of current-voltage characteristic does a capacitor have when fully charged?
a) Horizontal line
b) Vertical line
c) Exponential curve
d) S-shaped curve
Answer: a) Horizontal line
Hint: When fully charged, a capacitor acts like an open circuit, resulting in a constant voltage and zero current flow.
What is the current-voltage relationship of an inductor at a steady state?
a) Horizontal line
b) Vertical line
c) Exponential curve
d) S-shaped curve
Answer: b) Vertical line
Hint: At a steady state, an inductor acts like a short circuit, allowing current to flow freely and maintaining a constant voltage drop.
What type of current-voltage characteristic does a tunnel diode exhibit?
a) Exponential
b) Linear
c) Negative resistance
d) Quadratic
Answer: c) Negative resistance
Hint: Tunnel diodes demonstrate negative resistance in certain voltage ranges, leading to unique and unusual current-voltage characteristics.
How does the current change with voltage in a Zener diode beyond its breakdown voltage?
a) Linearly decreases
b) Exponentially decreases
c) Remains constant
d) Exponentially increases
Answer: c) Remains constant
Hint: Beyond the Zener diode’s breakdown voltage, it exhibits a constant voltage drop, maintaining a stable current.
What does a negative resistance region indicate in a current-voltage graph?
a) Unstable operation
b) Positive feedback
c) Decreasing current with increasing voltage
d) Inverted polarity
Answer: b) Positive feedback
Hint: Negative resistance regions are associated with positive feedback loops, leading to amplification in certain devices.
What is junction breakdown in a diode?
a) The point where the diode becomes open-circuited
b) The voltage at which the diode starts conducting current
c) The point where the reverse voltage causes a sudden increase in current
d) The voltage at which the diode stops conducting current
Answer: c) The point where the reverse voltage causes a sudden increase in current
Hint: Junction breakdown occurs in a diode when the reverse-biased voltage reaches a critical value, leading to a rapid rise in current.
What is the mechanism responsible for junction breakdown?
a) Avalanche effect
b) Thermal effect
c) Tunneling effect
d) Photoelectric effect
Answer: a) Avalanche effect
Hint: Junction breakdown is primarily caused by the avalanche effect, where electrons gain enough energy to create more electron-hole pairs through impact ionization.
What happens to the diode’s current in the breakdown region?
a) It decreases gradually
b) It remains constant
c) It increases linearly
d) It increases abruptly
Answer: d) It increases abruptly
Hint: In the breakdown region, the diode’s current increases sharply due to the avalanche multiplication of charge carriers.
What is the reverse breakdown voltage of a typical silicon diode?
a) 0.1 V
b) 1 V
c) 5 V
d) 100 V
Answer: d) 100 V
Hint: Silicon diodes usually have a reverse breakdown voltage in the range of tens to hundreds of volts.
What precautions should be taken to avoid permanent damage during junction breakdown?
a) Increase the forward voltage
b) Reduce the forward current
c) Limit the reverse voltage below the breakdown voltage
d) Increase the reverse current
Answer: c) Limit the reverse voltage below the breakdown voltage
Hint: To prevent permanent damage to the diode, the reverse voltage should not exceed the specified breakdown voltage.
What is the depletion region in a semiconductor device?
a) The region where free electrons and holes are generated
b) The region with no mobile charge carriers
c) The region where the device is operating in forward bias
d) The region with the maximum carrier concentration
Answer: b) The region with no mobile charge carriers
Hint: The depletion region is a region in a semiconductor device where all the mobile charge carriers are depleted, leaving behind immobile ions.
What creates the depletion region in a PN junction diode?
a) The flow of current
b) The diffusion of charge carriers
c) The presence of dopant atoms
d) The application of reverse bias voltage
Answer: d) The application of reverse bias voltage
Hint: When a reverse bias voltage is applied to a PN junction diode, it widens the depletion region by attracting the majority of carriers away from the junction.
What happens to the width of the depletion region in a PN junction diode under forward bias?
a) It increases
b) It decreases
c) It remains unchanged
d) It depends on the doping concentration
Answer: b) It decreases
Hint: Forward bias reduces the width of the depletion region by allowing the majority of carriers to flow across the junction.
In a PN junction diode under reverse bias, what effect does the depletion region have on the flow of current?
a) It enhances the current flow
b) It inhibits current flow
c) It has no effect on the current flow
d) It allows only minority carriers to flow
Answer: b) It inhibits current flow
Hint: The depletion region in a reverse-biased PN junction creates a potential barrier that opposes the flow of majority carriers, inhibiting current flow.
What is the primary role of the depletion region in a semiconductor device?
a) To amplify the incoming signal
b) To store charge carriers
c) To provide thermal insulation
d) To separate the regions of different doping concentrations
Answer: d) To separate the regions of different doping concentrations
Hint: The depletion region acts as a barrier separating the regions of different doping concentrations, creating a PN junction.
What type of charge carriers are typically present in the depletion region of a PN junction diode?
a) Majority carriers
b) Minority carriers
c) Free electrons only
d) Free holes only
Answer: b) Minority carriers
Hint: The depletion region contains immobile ions and a few minority carriers due to thermal generation.
What happens to the width of the depletion region with increasing reverse bias voltage in a PN junction diode?
a) It increases
b) It decreases
c) It remains constant
d) It depends on the temperature
Answer: a) It increases
Hint: Increasing the reverse bias voltage widens the depletion region, reducing the number of charge carriers near the junction.
What effect does temperature have on the depletion region width in a PN junction diode?
a) It increases the width
b) It decreases the width
c) It has no effect on the width
d) It depends on the material of the diode
Answer: c) It has no effect on the width
Hint: The width of the depletion region in a PN junction diode is primarily determined by the applied bias voltage and the doping concentration, not temperature.
What is the primary purpose of the depletion region in a photodiode?
a) To amplify the incoming light
b) To generate free electrons and holes
c) To absorb light photons
d) To create a potential barrier to separate charge carriers
Answer: d) To create a potential barrier to separate charge carriers
Hint: In a photodiode, the depletion region creates a potential barrier that separates the photogenerated charge carriers, leading to photocurrent flow.
How does the depletion region affect the capacitance of a PN junction diode?
a) It increases the capacitance
b) It decreases the capacitance
c) It has no effect on the capacitance
d) It depends on the operating frequency
Answer: b) It decreases the capacitance
Hint: The presence of the depletion region reduces the effective area for charge storage, leading to a decrease in the capacitance of a PN junction diode
What is the main application of the Zener diode?
a) Rectification
b) Amplification
c) Voltage regulation
d) Switching
Answer: c) Voltage regulation
Hint: Zener diodes are commonly used for voltage regulation due to their precise breakdown characteristics.
Which type of junction breakdown occurs in Zener diodes?
a) Avalanche breakdown
b) Thermal breakdown
c) Tunneling breakdown
d) Photoelectric breakdown
Answer: a) Avalanche breakdown
Hint: Zener diodes exhibit avalanche breakdown when operated in reverse bias beyond their breakdown voltage.
In a Zener diode, what happens to the current when the reverse voltage exceeds the breakdown voltage?
a) It decreases linearly
b) It remains constant
c) It decreases abruptly
d) It increases abruptly
Answer: b) It remains constant
Hint: Zener diodes maintain a nearly constant current beyond the breakdown voltage, making them suitable for voltage regulation.
What can happen if a diode is subjected to an excessive reverse voltage beyond its breakdown rating?
a) It becomes open-circuited
b) It emits light
c) It conducts high current
d) It can be permanently damaged
Answer: d) It can be permanently damaged
Hint: Subjecting a diode to an excessive reverse voltage beyond its breakdown rating can lead to permanent damage due to excessive current flow.
What is the primary use of avalanche diodes?
a) RF signal amplification
b) Temperature sensing
c) Protection against voltage spikes
d) Optical communication
Answer: c) Protection against voltage spikes
Hint: Avalanche diodes are used as transient voltage suppressors to protect electronic circuits from voltage spikes and transients
What type of current-voltage characteristic does a light-emitting diode (LED) exhibit?
a) Linear
b) Quadratic
c) Exponential
d) S-shaped curve
Answer: c) Exponential
Hint: LEDs follow an exponential relationship between current and voltage, similar to regular diodes.
How does the current-voltage characteristic of a photodiode change with light intensity?
a) Linearly increases
b) Quadratically increases
c) Exponentially increases
d) Remains constant
Answer: c) Exponentially increases
Hint: The current through a photodiode increases exponentially with light intensity, making them suitable for light detection applications
The barrier potential in a silicon p-n junction is approximately:
a) 0.3 V
b) 0.6 V
c) 1.1 V
d) 1.7 V
Answer: b
Hint: Silicon p-n junctions have a barrier potential of around 0.6 V.
The current in a p-n junction diode is mainly due to:
a) Electrons
b) Holes
c) Protons
d) Neutrons
Answer: b
Hint: In forward bias, holes dominate the current flow.
What is the minority carrier in the p-region of a forward-biased p-n junction?
a) Electrons
b) Holes
c) Protons
d) Neutrons
Answer: a
Hint: In forward bias, minority carriers are electrons in the p-region.
The reverse saturation current in a p-n junction diode:
a) Increases in temperature
b) Decreases with temperature
c) Remains constant with temperature
d) Becomes zero at absolute zero temperature
Answer: a
Hint: Reverse saturation current is temperature-dependent.
The process of combining p-type and n-type semiconductors to create a p-n junction is called:
a) Biasing
b) Doping
c) Diffusion
d) Fabrication
Answer: b
Hint: Doping introduces impurities into the semiconductor.
The breakdown voltage in a Zener diode is determined by:
a) Doping concentration
b) Barrier potential
c) Impurity atoms
d) Applied voltage
Answer: a
Hint: Higher doping concentrations result in lower breakdown voltages.
A p-n junction diode acts as a non-linear device because:
a) It has a linear I-V curve
b) Its resistance remains constant
c) Its I-V curve is not a straight line
d) It follows Ohm’s law
Answer: c
Hint: The I-V curve of a p-n junction is exponential, not linear.
In reverse bias, the width of the depletion region in a p-n junction:
a) Increases
b) Decreases
c) Remains the same
d) Becomes zero
Answer: a
Hint: Reverse bias widens the depletion region.
The breakdown of a Zener diode occurs due to:
a) Avalanche breakdown
b) Tunneling effect
c) Zener effect
d) Barrier breakdown
Answer: c
Hint: The Zener effect causes a breakdown in Zener diodes.
The I-V characteristics of a forward-biased p-n junction diode show that the current:
a) Increases rapidly with voltage
b) Increases linearly with voltage
c) Decreases rapidly with voltage
d) Remains constant with voltage
Answer: a
Hint: In forward bias, current increases exponentially with voltage.
In a p-n junction diode, holes move from the p-region to the n-region when:
a) A reverse bias is applied
b) A forward bias is applied
c) No bias is applied
d) The diode is heated
Answer: b
Hint: Forward biasing allows the current flow of holes from p to n.
The doping concentration in a p-n junction diode affects its:
a) Barrier potential
b) Breakdown voltage
c) Depletion region width
d) All of the above
Answer: d
Hint: Doping concentration influences various characteristics of the diode
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