Modern Physics - Semiconductor Electronics
Q. In a PN junction diode, what happens when it is forward biased? (2019)
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A.
Depletion region widens
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B.
Depletion region narrows
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C.
No current flows
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D.
Reverse current increases
Solution
When a PN junction diode is forward biased, the depletion region narrows, allowing current to flow.
Correct Answer: B — Depletion region narrows
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Q. What is the effect of temperature on the conductivity of intrinsic semiconductors? (2021)
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A.
Conductivity decreases
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B.
Conductivity remains constant
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C.
Conductivity increases
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D.
Conductivity becomes zero
Solution
As temperature increases, more electrons gain enough energy to jump the band gap, increasing conductivity.
Correct Answer: C — Conductivity increases
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Q. What is the energy band gap of a typical semiconductor? (2021)
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A.
0.1 eV
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B.
1.1 eV
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C.
2.0 eV
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D.
3.5 eV
Solution
The energy band gap of a typical semiconductor like silicon is approximately 1.1 eV.
Correct Answer: B — 1.1 eV
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Q. What is the function of a diode in a circuit? (2020)
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A.
To store energy
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B.
To amplify signals
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C.
To allow current to flow in one direction
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D.
To resist current flow
Solution
A diode allows current to flow in one direction only, acting as a one-way valve for electric current.
Correct Answer: C — To allow current to flow in one direction
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Q. What is the role of doping in semiconductors? (2022)
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A.
To increase resistance
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B.
To decrease conductivity
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C.
To introduce charge carriers
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D.
To create a magnetic field
Solution
Doping introduces additional charge carriers (electrons or holes) into the semiconductor, enhancing its conductivity.
Correct Answer: C — To introduce charge carriers
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Q. Which of the following is a characteristic of a Zener diode? (2019)
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A.
Used for rectification
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B.
Operates in reverse bias
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C.
Has a high forward voltage drop
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D.
Acts as a switch
Solution
A Zener diode is designed to operate in reverse bias and maintain a constant voltage.
Correct Answer: B — Operates in reverse bias
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Q. Which of the following is a p-type semiconductor? (2020)
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A.
Silicon doped with phosphorus
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B.
Silicon doped with boron
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C.
Germanium doped with arsenic
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D.
Gallium nitride
Solution
Boron is a trivalent element that creates holes in silicon, making it a p-type semiconductor.
Correct Answer: B — Silicon doped with boron
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