Mechatronics Questions and Answers – Solid State Electronic Devices – PN Junction Diode

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This set of Mechatronics Multiple Choice Questions & Answers (MCQs) focuses on “Solid State Electronic Devices – PN Junction Diode”.

1. How many PN junctions is/are present in a bipolar junction transistor?
a) 0
b) 1
c) 2
d) 3
View Answer

Answer: c
Explanation: A bipolar junction transistor (BJT) contains 2 PN junctions. If the transistor is NPN type then it contains a P-type semiconductor sandwiched between two N-type semiconductor. If the transistor is PNP type then it contains a N-type semiconductor sandwiched between two P-type semiconductor. In both the cases there are two PN junctions.

2. What are the majority charge carriers in P-type semiconductors?
a) Electrons
b) Holes
c) Negative Ions
d) Positive Ions
View Answer

Answer: b
Explanation: Holes are the majority charge carriers in P-type semiconductors. These holes are actually electron vacancies that contain positive charge. The holes are responsible for the conduction in p-type semiconductors.

3. What are present at the potential barrier of a PN junction when no external voltage is applied?
a) Electrons
b) Holes
c) Positive Ions
d) Positive and Negative Ions
View Answer

Answer: d
Explanation: Positive and Negative Ions are present at the potential barrier of a PN junction when no external voltage is applied. These Ions are immobile and are accumulated which does not allow the electrons and holes to cross the junction until an external voltage is applied.
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4. Which is an example of Schottky diode?
a) MSP430G2ET
b) CMCP793V-500
c) SLB700A/06VA
d) MBR5H100MFST1G
View Answer

Answer: d
Explanation: MBR5H100MFST1G is an example of Schottky diode. Schottky diodes are most common PN junction diodes used in analog electronics. It is a simple diode that contain P and N junction but has a fast switching action and a low forward voltage drop.

5. Ions do not move in a PN junction.
a) True
b) False
View Answer

Answer: a
Explanation: Ions does not move in a PN junction. They are immobile. They are created due to the absence of charge carriers at a position. If an electron moves from one place to another, then it leaves behind a vacancy which is positively charged. This vacancy is called Positive Ion.

6. When the p-type semiconductor is connected to positive terminal and n-type to negative terminal of a PN junction diode then the diode is said to be reverse biased.
a) True
b) False
View Answer

Answer: b
Explanation: When the p-type semiconductor is connected to positive terminal and n-type to negative terminal of a PN junction diode then the diode is said to be forward biased. In forward biased configuration the holes start to move towards N type semiconductor and the electrons towards P type semiconductor, this leads to flow of current in the diode.

7. What is the minimum voltage required to make the PN junction of a real silicon transistor in forward biased?
a) 0.7 volts
b) 0.8 volts
c) 0.9 volts
d) 0.3 volts
View Answer

Answer: a
Explanation: 0.7 volts is the minimum voltage required to make the PN junction of a real silicon transistor in forward biased. This 0.7 volt potential difference makes the PN junction between base and emitter terminal in forward biased.
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8. Which is an example of PN junction diode?
a) Light Emitting Diode
b) Light dependent resistor
c) Photo Voltaic cell
d) Capacitor
View Answer

Answer: a
Explanation: Light Emitting Diode (LED) is an example of PN junction diode. A layer of Phosphor is added at the junction who is responsible for the glow. Phosphor is a substance that exhibits the phenomenon of luminescence.

9. What are the parameters over which a diode characteristics curve is made?
a) Current and time
b) Voltage and time
c) Current and frequency
d) Voltage and current
View Answer

Answer: d
Explanation: Voltage and current are the parameters considering which a diode characteristics curve is made. It is voltage versus current graph in which Current is denoted on Y-axis and voltage is denoted on (X-axis).
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10. What are the majority charge carriers in N-type semiconductors?
a) Electrons
b) Holes
c) Negative Ions
d) Positive Ions
View Answer

Answer: a
Explanation: Electrons are the majority charge carriers in N-type semiconductors. When a potential difference is created across the terminals of semiconductor, the electrons starts to move, these free electrons are responsible for the conduction in N-type semiconductors.

11. What happens when a trivalent semiconductor is doped with a pure semiconductor?
a) N-Type extrinsic semiconductor is formed
b) P-Type extrinsic semiconductor is formed
c) PN junction is formed
d) NP junction is formed
View Answer

Answer: b
Explanation: P-Type extrinsic semiconductor is formed when a trivalent semiconductor is doped with a pure semiconductor. Holes are the majority charge carriers in P-type semiconductor, whereas electrons are majority charge carriers in N type semiconductors.

12. What happens when a pentavalent semiconductor is doped with a pure semiconductor?
a) N-Type extrinsic semiconductor is formed
b) P-Type extrinsic semiconductor is formed
c) PN junction is formed
d) NP junction is formed
View Answer

Answer: a
Explanation: N-Type extrinsic semiconductor is formed when a pentavalent semiconductor is doped with a pure semiconductor. Electrons are the majority charge carriers in N-type semiconductor, whereas holes are majority charge carriers in P type semiconductors.

13. Which impurity should be added to pure semiconductor to make a P-type semiconductor?
a) Arsenic
b) Phosphorus
c) Boron
d) Antimony
View Answer

Answer: c
Explanation: Boron should be added to pure semiconductor to make a P-type semiconductor. P-Type extrinsic semiconductor is formed when a trivalent semiconductor is doped with a pure semiconductor. Boron is a trivalent compound whereas all others are pentavalent compound.

14. Which impurity should be added to pure semiconductor to make an N-type semiconductor?
a) Gallium
b) Phosphorus
c) Indium
d) Aluminum
View Answer

Answer: b
Explanation: Aluminum should be added to pure semiconductor to make a N-type semiconductor. N-Type extrinsic semiconductor is formed when a pentavalent semiconductor is doped with a pure semiconductor. Phosphorus is a pentavalent compound whereas all others are trivalent compound.

15. PN junction can be made by physically joining P type and N type semiconductor.
a) True
b) False
View Answer

Answer: b
Explanation: PN junction cannot be made by physically joining P type and N type semiconductor. Even when P type and N type materials are held firmly then also huge microscopic gaps are present between both the semiconductors which does not allow holes and electrons to pass through it.

Sanfoundry Global Education & Learning Series – Mechatronics.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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