Exercise: Electronic Devices And Circuits

Questions for: Electronic Devices And Circuits

An air gap provided in the iron core of an inductor prevents
A:
flux leakage
B:
hysteresis loss
C:
core saturation
D:
heat generation
Answer: C
No answer description is available. Let's discuss.
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An increase in junction temperature of a semiconductor diode
A:
causes a small increase in reverse saturation current
B:
causes a large increase in reverse saturation current
C:
does not affect reverse saturation current
D:
may cause an increase or decrease in reverse saturation current depending on rating of diode
Answer: B

Reverse saturation current doubles for every 10°C rise in junction temperature.

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In which device does the extent of light controls the conduction
A:
photovoltaic cell
B:
photo electric relay
C:
LED
D:
photo sensitive device
Answer: D

The resistance of photosensitive device depends on the light.

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The threshold voltage of a MOSFET can be lowered by
  1. using thin gate oxide
  2. reducing the substrate concentration
  3. increasing the substrate concentration.
Of the above statement
A:
3 alone is correct
B:
1 and 2 are correct
C:
1 and 3 are correct
D:
2 alone is correct
Answer: C

Increasing the substrate concentration lowers threshold voltage. Gate oxide layer has no effect an threshold voltage.

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An n type silicon bar 0.1 cm long and 100 Ξm2 in cross-sectional area has a majority carrier concentration of 5 x 1020/m3 and the carrier mobility is 0.13 m0/V-s at 300k. If the charge of an electron is 1.6 x 10-19 coulomb, then the resistance of the bar is
A:
106 ohm
B:
104 ohm
C:
10-1 ohm
D:
10-4 ohm
Answer: C

Resistance of bar(R) =

l = 0.1 cm, A = 100 x 10-6 m2

σ = neΞn + PeΞp

But bar is of n type then it can be approximated to σ = neΞn.

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