GATE EC||ELECTRONIC DEVICES AND CIRCUIT||PYQs(2000-2025)

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Question 1

The band gap of silicon at 300 K is

(GATE 2006 || EC || MCQ ||1 MARK)

  • 1.36 eV

  • 1.10 eV

  • 0.80 eV

  • 0.67 eV

Question 2

n-type silicon is obtained by doping silicon with

(GATE 2006 || EC || MCQ ||1 MARK)

  • Germanium

  • Aluminum

  • Boron

  • Phosphorus

Question 3

The intrinsic carrier concentration of a silicon sample at 300 K is 1.5 × 10 16 /m 3 . If after doping, the number of majority carriers is 5 × 10 20 /m 3 , the minority carrier

(GATE 2003 || EC || MCQ ||1 MARK)

  • 4.50 × 10 11/m 3

  • 3.33 × 10 4 /m 3

  • 5.00 × 10 20/m 3

  • 3.00 ×10 –5 /m 3

Question 4

An n-type silicon bar 0.1 cm long and 100µm2  in the cross-sectional area has a majority carrier concentration of 5 × 1020 /m 3  and the carrier mobility is 0.13 m2 /V–s at 300 K. If the charge of an electron is 1.6 × 10–19  coulomb, then the resistance of the bar is


(GATE 2003 || EC || MCQ || 1 MARK)

  • 10 6  ohm

  • 104 ohm

  • 10-1 ohm

  •  10–10  ohm

Question 5

The electron concentration in a sample of uniformly doped n-type silicon at 300 K varies linearly from 1017/cm 3 at x = 0 to 6×1016 /cm 3 at x = 2µm. Assume a situation that electrons are supplied to keep this concentration gradient constant with time. If the electronic charge is 1.6 × 1019 coulomb and the diffusion constant Dn = 35 cm2/s, the current density in the silicon if no electric field is present?


(GATE 2003 || EC || MCQ ||1 MARK)

  •  zero

  • -1112 A/cm

  • +1120 A/cm 2

  • -1120 A/cm 2

Question 6

Under low level injection assumption, the injected minority carrier current for an extrinsic semiconductor is essentially the


(GATE 2006 || EC || MCQ ||1 MARK)

  • diffusion current

  • drift current

  • recombination current

  • induced current

Question 7

The majority carrier in an n-type semiconductor has an average drift velocity v in a direction perpendicular to a uniform magnetic field B. The electric field E induced due to Hall effect acts in the direction

(GATE 2006 || EC || MCQ ||1 MARK)

  • v × B

  • B × v

  • along v

  • opposite to v

Question 8

A heavily doped n-typed semiconductor has the following data. Hole-electron mobility ratio: 0.4 Doping concentration: 4.2 × 108 atoms/ m 3 .Intrinsic concentration: 1.5 × 104 atoms/ m3. The ratio of conductance of the n-type semiconductor to that of the intrinsic semiconductor of same material and at the same temperature is given by

(GATE 2006 || EC || MCQ ||1 MARK)

  • 0.00005

  • 2,000

  • 10,000

  • 20,000

Question 9

The concentration of minority carriers in an extrinsic semiconductor under equilibrium is

(GATE 2006 || EC || MCQ ||1 MARK)

  • directly proportional to the doping concentration

  • inversely proportional to the doping concentration

  • directly proportional to the intrinsic concentration

  • inversely proportional to the intrinsic concentration

Question 10

The resistivity of a uniformly doped n-type silicon sample is 0.5Ω– cm. If the electron mobility (μ n ) is 1250 cm2 /V–sec and the charge of an electron is 1.6 × 10–19 Coulomb, the donor impurity concentration (ND ) is

(GATE 2004 || EC || MCQ || 1 MARK)

  • 2 × 1016 /cm3

  • 1 × 1016 /cm3

  • 2.5 × 1015 /cm3

  • 2 × 1015 /cm3

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