Electronic Devices And Circuits MCQ Questions & Answers

61

The semiconductor bar is heated at one end, a voltage across the bar is developed. If the heated end is positive, the semiconductor is

A) P-type B) N-type C) Intrinsic D) Highly degenerated

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Answer & Solution

Answer: Option B

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62

In PN-junction diode, if doping concentration of acceptor atoms in P-region is increased then

A) depletion width in N-region will increase and contact potential will decrease B) depletion width in P-region and N-region will decrease while contact potential remains constant C) depletion width in P-region will decrease and contact potential will increase D) None of the above

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Answer & Solution

Answer: Option C

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63

The output current versus input voltage transfer characteristics of an n-channel JFET is such that there is

A) zero current flow at zero input voltage bias B) current flow only when a positive input threshold voltage is crossed C) current flow only when a negative input cut-off voltage bias is crossed D) no cut-off input voltage

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Answer & Solution

Answer: Option C

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64

Which of the following is correct?

A) Intrinsic and extrinsic semiconductors have negative temperature coefficient and conductors have positive temperature coefficient B) Conductors and extrinsic semiconductors have negative temperature coefficient and intrinsic semiconductors have positive temperature coefficient C) Insulators and semiconductors have positive temperature coefficient whereas conductors have negative temperature coefficient D) Conductors and extrinsic semiconductors have positive temperature coefficient and pure semiconductors have negative temperature coefficient

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Answer & Solution

Answer: Option D

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65

Identify the correct statement about MOS capacitor-

A) For an N-type substrate, a negative voltage is applied and accumulation occurs B) For a P-type substrate, a negative voltage is applied and accumulation occurs C) For an N-type substrate, a positive voltage is applied and accumulation occurs D) For a P-type substrate, a positive voltage is applied and an N-type inversion layer is formed

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Answer & Solution

Answer: Option D

Solution:

A MOS capacitor consists of a metal gate, oxide layer, and semiconductor substrate. The behavior of the surface region depends on the type of substrate and the polarity of the applied gate voltage.

For a P-type substrate with positive gate voltage: The applied positive potential repels holes (majority carriers) away from the surface and attracts electrons (minority carriers) towards the oxide–semiconductor interface. This leads to the formation of an N-type inversion layer. Hence, Option D is correct.

Option A: Incorrect, because in an N-type substrate under negative voltage, holes move towards the surface causing accumulation, not inversion.

Option B: Incorrect, because in a P-type substrate with negative voltage, holes are attracted to the surface, again causing accumulation, not inversion.

Option C: Incorrect, because in an N-type substrate with positive voltage, electrons accumulate at the surface, leading to accumulation only, not inversion.

Therefore, the correct statement is Option D.

66

. . . . . . . . of the varactor-diode changes with the change in applied voltage.

A) Resistance B) Reactance C) Concentration of carrier D) Temperature

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Answer & Solution

Answer: Option B

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67

The reverse saturation current of a silicon diode doubles for every

A) 10°K rise in temperature B) 10°C rise in temperature C) 2°C rise in temperature D) 10°F rise in temperature

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Answer & Solution

Answer: Option B

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68

The leakage current in CE configuration may be around

A) Few nanoampers B) Few microampers C) Few hundred microampers D) Few milliamperes

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Answer & Solution

Answer: Option C

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69

For the 2N338 transistor, the manufacturer specifies P_max = 100 mW at 25°C free air temperature and the maximum junction temperature, T_jmax = 125°C. Its thermal resistance is

A) 10°C/W B) 100°C/W C) 1000°C/W D) 10,000°C/W

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Answer & Solution

Answer: Option C

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70

The band gap energies for silicon and germanium photodiodes are 1.1 eV and 0.67 eV respectively, their cutoff wavelength respectively would be:

A) 1127.27 nm, 1850.75 nm B) 1850.27 nm, 2167.91 nm C) 456.12 nm, 1127.27 nm D) 1315.45 nm, 1850.75 nm

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Answer & Solution

Answer: Option A

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Electronic Devices And Circuits MCQ Questions & Answers | ECE