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Electronics Engineering Objective Questions { Semiconductor Physics and Diodes }

204. The resistivity of a uniformly doped n-type silicon sample is 0.5 a-cm. If the electron mobility (N) is 1250 cm2N-sec and the charge of an electron is 1.6 x 10-19 Coulomb, the donor impurity concentration (ND) in the sample is
A. 2 x 1016/cm3
B. 1 x 1016/cm3
C. 2.5 x 1015/cm3
D. 2 x 1015/cm3
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205. The bandgap of Silicon at room temperature is
A. 1.3 eV
B. 0.7 eV
C. 1.1 eV
D. 1.4 eV
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206.  A Silicon PN junction at a temperature of 20?C has a reverse saturation current of 10 pico-Amperes (pA). The reverse saturation current at 40?C for the same bias is approximately
A. 30 pA
B. 40 pA
C. 50 pA
D. 60 pA
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207. The primary reason for the widespread use of Silicon in semiconductor device technology is
A. aboundance of Silicon on the surface of the Earth.
B. large bandgap of Silicon in comparison to Germanium.
C. favorable properties of Silicon-dioxide (Si02).
D. lower melting point
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208.  Refractive index of glass is 1.5. Find the wavelength of a beam of light with a frequency of 1014 Hz in glass. Assume velocity of light is 3 x 108 m/s in vacuum.
A. 3 gm
B. 3 mm
C. 2 gm
D. 1 gm
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209. A Silicon sample A is doped with 1018 atoms/cm3 of Boron. Another sample B of identical dimensions is doped with 1018 atoms/cm3 of Phosphorus. The ratio of electron to hole mobility is 3. The ratio of conductivity of the sample A to B is
A. 3: 1
B. 3:2
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210. A Silicon PN junction diode under reverse bias has depletion region of width 10am. The relative permittivity of Silicon, Cr = 11.7 and the permittiveity of free space Co = 8.85 x 10-12 F/m. The depletion capacitance of the diode per square meter is
A. 100 RF.
B. 10 pF.
C. 1 tiF
D. 20 uF..
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