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Semiconductor Devices and Transistor Fundamentals

Concept-based questions on semiconductor physics, p-n junctions, and bipolar junction transistor operation and characteristics

15 Questions Published
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Questions

Question 1 Multiple Choice (Single Answer)

The resistivity of an intrinsic semiconductor decreases with increasing temperature. This is because with increasing temperature,

  1. Both the carrier concentration and mobility of carriers decrease
  2. The carrier concentration increases but the mobility of carriers decreases
  3. The carrier concentration decreases but the mobility of carriers increases
  4. The carrier concentration remains the same but the mobility of carriers decreases
  5. None of these
Question 2 Multiple Choice (Single Answer)

The depletion region of a p-n junction has

  1. Electrons and holes
  2. Positive ions and electrons
  3. Positive ions and negative ions
  4. No ions, electrons or holes
  5. None of these
Question 3 Multiple Choice (Single Answer)

In a p-n junction, to make the depletion region extend prominently into p-region, the concentration of impurities in the p-region must be

  1. Much less than the concentration of impurities in n-region
  2. Much higher than the concentration of impurities in n-region
  3. Equal to the concentration of impurities in n-region
  4. Zero
  5. None of these
Question 4 Multiple Choice (Single Answer)

When the reverse voltage across a p-n junction is gradually decreased, the depletion region

  1. Does not change in width
  2. Initially increases up to a certain width and then decreases
  3. Continuously increases in width
  4. Continuously decreases in width
  5. None of these
Question 5 Multiple Choice (Single Answer)

In an unbiased p-n junction, the junction current at equilibrium is

  1. Due to the diffusion of minority carriers only
  2. Due to the diffusion of majority carriers only
  3. Zero because equal and opposite drift and diffusion currents for electrons and holes cross the junction
  4. Zero because no charge crosses the junction
  5. None of these
Question 6 Multiple Choice (Single Answer)

In an intrinsic semiconductor, the electron and hole densities are equal at

  1. 0 K
  2. 0oC
  3. High temperature
  4. All temperatures
  5. None of these
Question 7 Multiple Choice (Single Answer)

In an unbiased p-n junction, the thickness of the depletion region is of the order of

  1. 0.005 μm
  2. 0.5 μm
  3. 5 mm
  4. 10-10 m
  5. None of these
Question 8 Multiple Choice (Single Answer)

The emitter of a transistor is generally doped most heavily because it

  1. Has to dissipate the maximum power
  2. Has to supply the charge carriers
  3. Is the first region of the transistor
  4. Must possess low resistance
  5. None of these
Question 9 Multiple Choice (Single Answer)

The fermi level in a p-semiconductor lies close to

  1. The top of the valence band
  2. The top of the conduction band
  3. The bottom of the valence band
  4. The bottom of the conduction band
  5. None of these
Question 10 Multiple Choice (Single Answer)

A small increase in the collector reverse bias will cause

  1. A large increase in the emitter current
  2. A large increase in the collector current
  3. A large decrease in the collector current
  4. A very small change in collector reverse saturation current
  5. None of these
Question 11 Multiple Choice (Single Answer)

Which of the following transistor configuration circuits is much less temperature dependent?

  1. Common base
  2. Common emitter
  3. Common collector
  4. Common source JFET
  5. None of these
Question 12 Multiple Choice (Single Answer)

Which of the following statements is not correct for emitter follower circuit?

  1. It raises the power level.
  2. It exhibits high input impedance and low output impedance.
  3. It has high current gain.
  4. It has high voltage gain.
  5. None of these
Question 13 Multiple Choice (Single Answer)

A transistor is said to be in a quiescent stage when

  1. The emitter junction bias is just equal to the collector junction bias
  2. No currents are flowing
  3. No signal is applied to the input
  4. It is unbiased
  5. None of these
Question 14 Multiple Choice (Single Answer)

Early effect in BJT refers to

  1. Avalanche breakdown
  2. Thermal runway
  3. Base narrowing
  4. Zener breakdown
  5. None of these
Question 15 Multiple Choice (Single Answer)

Conduction electrons in a semiconductor have higher mobility than holes because they

  1. Have negative charge
  2. Are lighter
  3. Experience collisions less frequently
  4. Need less energy to move them
  5. None of these
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