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Electronic Devi...

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  • Question 1
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    Which of the following is n-type semiconductor?

  • Question 2
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    Consider an abrupt p-n junction at T = 300 K with doping concentrations of Nd = 3 × 1016 cm-3 and Na = 4 × 1015 cm-3. At zero bias, the depletion region extending to the p-side is 0.447 μm. The depletion region extending to the n-side will be:

  • Question 3
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    Which of the following can be used in the fabrication of p-type semiconductor?

  • Question 4
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    For P-type semiconductor, the dopant is

  • Question 5
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    Doping material for p-type semiconductor is:

  • Question 6
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    Gradual flow of charge from a region of high density to a region of low density is called _________.

  • Question 7
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    A GaAs LED radiates at wavelength 900 nm. If the current through the LED is 20 mA, the output optical power, with an internal quantum efficiency of 10% is ________ mW

  • Question 8
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    The ratio of hole minority current to the electron minority current in an infinite p-n junction is 4. If conductivity on p-side is 1.4 S/cm and on n-side is 2.8 S/cm, then the ratio of diffusion length Ln and Lp (ie Ln/Lp) is _______.

  • Question 9
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    An n–type silicon sample of 10–3 m length and 10–10 m2 cross sectional area has an impurity concentration of 5 × 1020 atom/m3. If mobility of majority carries is 0.125 m2/v-sec, then the resistance of the sample will be ________.

  • Question 10
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    Calculate the hall voltage when the magnetic field is 8 A/m, current is 4 A, width is 5 m and the concentration of carrier is 10²⁰

  • Question 11
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    In a semiconductor, Drift current is due to:

  • Question 12
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    According to Einstein’s relationship for a semiconductor, the ratio of the diffusion constant to the mobility of the charge carriers is

  • Question 13
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    Consider two pnp bipolar junction transistors. For first transistor when emitter to collector voltage is 5 V, VEB is 0.85 V and emitter current is 10 A. (The β for this transistor is 15). Second BJT conducts with collector current of 1 mA and VEB = 0.70. The ratio of emitter base junction area of first transistor to second transistor is ______.

    (Assume KT = 26 mV)

  • Question 14
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    The unit of mobility is

  • Question 15
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    If EgE denotes the bandgap of emitter and EgB denotes the Bandgap of Base. Then in order to achieve high gain β pf the transistor

  • Question 16
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    If temperature will increase, the conductivity of semiconductor will:

  • Question 17
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    Hall effect can be used to measure

  • Question 18
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    A sample of GaAs doped with NA = 1017 cm-3. For GaAs, intrinsic concentration is ni = 2.2 × 106 cm-3, mobility of electron is μn = 5300 cm2 / V-sec, and mobility of hole is μp = 230 cm2 / V sec.

    If the sample is illuminated, an excess electron concentration of 1016 cm-3 is generated.

    Based on the above information, which of the following statements is/are correct?

  • Question 19
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    A depletion type N-channel MOSFET is biased in its linear region for use as a voltage controlled resistor. Assume threshold voltage VTH = 0.5 V, VGS = 2.0 V, VDS = 5 V, W/L = 100, COX = 10-8 F/cm2 and μn = 800 cm2/V-s. The value of the resistance of the voltage controlled resistor (in Ω) is _________.

  • Question 20
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    On applying an electric field of intensity 10 V/cm across a semiconductor at a certain temperature the average drift velocity of free electrons is measured to be 70 m/s. Then the electron mobility is

  • Question 21
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    The diffusion capacitance of a germanium PN junction diode is 10 nF at forward voltage of 0.5 V, then the diffusion capacitance of same PN diode at applied voltage of 1 V is.

    Take η = 1, VT = 0.0259 V

  • Question 22
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    Consider an LED made of a semiconductor with \({E_g} =\sqrt{1.24}~eV\) and \(\frac{{d{E_g}}}{{dT}}\) = -5× 10-4 eV/K. The change in the emitted wavelength if the temperature changes by 10°C is:

    (Take hc = 1240 eV nm)

  • Question 23
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    A T = 300 K, an n-type silicon sample contains a donor concentration Nd = 1016 cm-3 and intrinsic concentration ni = 1.5 × 1010 cn-3. The minority carrier hole lifetime is found to be τp0 = 20 μs.

    Which of the following conclusions for the given data is/are correct?

  • Question 24
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    The finer resolution in lithography can be obtained using

  • Question 25
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    The resistivities of the two sides of an abrupt germanium diode are 2 Ω-cm (p side) and 1 Ω-cm (n side) at 300 K. Assume that the mobility of electrons and holes in germanium is μn = 3800 cm2 / V-sec and μp = 1800 cm2 / V-sec respectively, and intrinsic concentration ni = 2.25 × 1013 cm-3. Take kT = 25.9 meV. The value of built-in potential (in volt) is________. (Correct up to 2 decimal places)

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