JEE Questions for Physics Semiconductor Devices Quiz 3 - MCQExams.com

A valanche breakdown in a p-n junction diode is due to
  • sudden shift of Fermi level
  • increase in the width of forbidden gap
  • sudden increase of impurity concentration
  • cumulative effect of increased electron collision and creation of added electron-hole pairs
An electron-hole pair is formed when light of maximum wavelength 6000 Å is incident on the semiconductor. What is the bond gap energy of the semiconductor?
( h = 6.62 × 10-34 J-s )
  • 3.31 × 10-19 J
  • 3.07 × 10-19 J
  • 2.07 × 10-19 J
  • 2.07 J
In the following circuit, the current flowing through 1 kΩ resistor is
Physics-Semiconductor Devices-87447.png
  • zero
  • 5 mA
  • 10 mA
  • 15 mA
  • 20 mA
For a common emitter amplifier, the audio signal voltage across the collector resistance 2 kΩ is 2V. If the current amplification factor of the transistor is 220, and the base resistance is 1.5Ω, the input signal voltage and base current are
  • 0.1 V and 1µA
  • 0.15 V and 10µA
  • 1.015 V and 1 A
  • 0.0015 V and 1 mA
  • 0.0075 V and 5µA
The graph given below represents the I-V characteristics of a zener diode. Which part of the characteristics curve is most relevant for its operation as a voltage regulator?
Physics-Semiconductor Devices-87448.png
  • ab
  • bc
  • cd
  • de
The reverse saturation of p-n diode
  • depends on doping concentrations
  • depends on diffusion lengths of carriers
  • depends on the doping concentrations and diffusion lengths
  • depends on the doping concentrations, diffusion length and device temperature
In semiconductors at a room temperature,
  • the valence band is partially empty and the conduction band is partially filled
  • the valence band is completely filled and tile conduction band is partially filled
  • the valence band is completely filled
  • the conduction band is completely empty
A p-n photodiode is made of a material with a band gap of 2.0 eV, The minimum frequency of the radiation that can be absorbed by the material is nearly
  • 10 × 1014 Hz
  • 5 × 1014 Hz
  • 1 × 1014 Hz
  • 20 × 1014 Hz
A reverse biased diode is

  • Physics-Semiconductor Devices-87449.png
  • 2)
    Physics-Semiconductor Devices-87450.png

  • Physics-Semiconductor Devices-87451.png

  • Physics-Semiconductor Devices-87452.png
In an unbiased p-n junction
  • potential at p is more than that at n
  • potential at p is less than that at n
  • potential at p is equal to that at n
  • potential at p is +ve and that at n is -ve
The current I through 10 Ω resistor in the circuit given below is
Physics-Semiconductor Devices-87453.png
  • 50 mA
  • 20 mA
  • 40 mA
  • 80 mA
  • 35 mA
A Si and Ge diode has identical physical dimensions. The band gap in Si is larger than that in Ge. An identical reverse bias is applied across the diodes
  • the reverse current in Ge is larger than that in Si
  • the reverse current in Si is larger than that in Ge
  • the reverse current is identical in the two diodes
  • the relative magnitude of the reverse currents cannot be determined from the given data only
The charge carriers in a p -type semiconductor are
  • electrons only
  • holes only
  • holes in larger numbers and electrons in smaller numbers
  • holes and electrons in equal numbers
The electrical conductivity of an intrinsic semiconductor at 0 K is
  • less than that of an insulator
  • is equal to zero
  • is equal to infinity
  • more than that of an insulator
If nE and nH represent the number of free electrons and holes respectively in a semiconducting material, then for n- type semiconducting material
  • nE << nH
  • nE >> nH
  • nE = nH
  • nE = nH = 0
An intrinsic semiconductor at 0 K temperature behaves like
  • conductor
  • p -type semiconductor
  • n-type semiconductor
  • insulator
When a p -n junction diode is connected in forward bias its barrier potential
  • decreases and less current flows in the circuit
  • decreases and more current flows in the circuit
  • increases and more current flows in the circuit
  • decreases and no current flows in the circuit
The main cause of zener breakdown is
  • the base semiconductor being germanium
  • production of electron-hole pairs due to thermal excitation
  • low doping
  • high doping
The depletion layer in a silicon diode is 1 μm wide and its knee potential is 0.6 V, then the electric field in the depletion, layer will be
  • 0.6 Vm-1
  • 6 × 104 Vm-1
  • 6 × 104 Vm-1
  • zero
A Light Emitting Diode (LED) has a voltage drop of 2 V across it and passes a current of 10 mA. When it operates with a 6 V battery through a limiting resistor R, the value R is
  • 40 kΩ
  • 4 kΩ
  • 200 kΩ
  • 400 Ω
When a p-n junction diode is reverse biased, then
  • no current flows
  • the depletion region is increased
  • the depletion region is reduced
  • the height of the potential barrier is reduced
To a germanium crystal equal number of aluminium and indium atoms are added. Then
  • it remains an intrinsic semiconductor
  • it becomes a n-type semiconductor
  • it becomes a p-type semiconductor
  • it becomes an insulator
If in a p-n junction diode, a square input signal of 10 V is applied as shown in the figure
Physics-Semiconductor Devices-87456.png

  • Physics-Semiconductor Devices-87457.png
  • 2)
    Physics-Semiconductor Devices-87458.png

  • Physics-Semiconductor Devices-87459.png

  • Physics-Semiconductor Devices-87460.png
A conductor and a semiconductor are connected in parallel as shown in the figure. At a certain voltage both ammeters register the same current. If the voltage of the DC source is increased then the
Physics-Semiconductor Devices-87461.png
  • ammeter connected to the semiconductor will register higher current than the ammeter connected to the conductor
  • ammeter connected to the conductor will register higher current than the ammeter connected to the semiconductor
  • ammeters connected to both semiconductor and conductor will register the same current
  • ammeters connected to both semiconductor and conductor will register no change in the current
Minority carriers in a p-type semiconductor are
  • free electrons
  • holes
  • Neither holes nor free electrons
  • Both holes and free electrons
The difference in the variation of resistance with temperature in a metal and a semiconductor arises essentially due to the difference in the
  • crystal structure
  • variation of the number of charge carriers with temperature
  • type of bonding
  • variation of scattering mechanism with temperature
In the middle of the depletion layer of reverse biased p-n junction, the
  • electric field is zero
  • potential is maximum
  • electric field is maximum
  • potential is zero
In a reverse biased diode when the applied voltage changes by 1 V, the current is found to change by 0.5 μA. The reverse bias resistance of the diode is
  • 2 × 105 Ω
  • 2 × 106 Ω
  • 200 Ω
  • 2 Ω
A photodetector used to detect the wavelength of 1700 nm, has energy gap of about
  • 0.073 eV
  • 1.2 eV
  • 7.3 eV
  • 1.16 eV
  • 0.73 eV
The energy gap between conduction band and the valence band is of the order of 0.7 eV. Then it is
  • an insulator
  • a conductor
  • a semiconductor
  • an alloy
  • a superconductor
The depletion layer of a p-n junction
  • is of constant width irrespective of the bias
  • acts like an insulating zone under reverse bias
  • has a width that increases with an increase in forward bias
  • is depleted of ions
The current in the circuit shown in the figure, considering ideal diode is
Physics-Semiconductor Devices-87464.png
  • 20 A
  • 2 × 10-3 A
  • 200 A
  • 2 × 10-4 A
In depletion layer of unbiased p-n junction
  • holes are present
  • electrons are present
  • only fixed ions are present
  • None of the above
Why is there sudden increase in current in zener diode ?
  • Due to rupture of bonds
  • Resistance of depletion layer becomes less
  • Due to high doping
  • None of the above
In an n-type semiconductor, the fermi energy level lies
  • in the forbidden energy gap nearer to the conduction band
  • in the forbidden energy gap nearer to the valence band
  • in the middle of forbidden energy gap
  • outside the forbidden energy gap
The temperature of germanium is decreased from room temperature to 100 K, the resistance of germanium
  • decreases
  • increases
  • unaffected
  • depends on external conditions
The diode used in the circuit shown in the figure, has a constant voltage drop of 0.5 V at all currents and a maximum power rating of 100 milli-watt. What should be the value of the resistance R, connected in series with the diode, for obtaining maximum current ?
Physics-Semiconductor Devices-87466.png
  • 1.5 Ω
  • 5 Ω
  • 6.67 Ω
  • 200 Ω
When n-p-n transistor is used as an amplifier
  • electrons move from base to collector
  • holes move from emitter to base
  • electrons move from collector to base
  • holes move from base to emitter

Physics-Semiconductor Devices-87467.png

  • Physics-Semiconductor Devices-87468.png
  • 2)
    Physics-Semiconductor Devices-87469.png

  • Physics-Semiconductor Devices-87470.png

  • Physics-Semiconductor Devices-87471.png
The circuit has two oppositely connected ideal diodes in parallel. What is the current flowing in the circuit ?
Physics-Semiconductor Devices-87472.png
  • 1.71 A
  • 2.00 A
  • 2.31 A
  • 1.33 A
In the following, which one of the diodes is reverse biased ?

  • Physics-Semiconductor Devices-87474.png
  • 2)
    Physics-Semiconductor Devices-87475.png

  • Physics-Semiconductor Devices-87476.png

  • Physics-Semiconductor Devices-87477.png
Doping of intrinsic semiconductor is done
  • to neutralise charge carriers
  • to increase the concentration of majority charge carriers
  • to make it neutral before disposal
  • to carry out further purification
On increasing the reverse bias to a large value in a p-n junction, diode current
  • increases slowly
  • remains fixed
  • suddenly increases
  • decreases slowly
With in depletion region of p-n junction diode
  • p-side is positive and n-side is negative
  • p-side is negative and n-side is positive
  • Both sides are positive or both negative
  • Both side are neutral
In a forward biased p-n junction diode, the potential barrier in the depletion region is of the form

  • Physics-Semiconductor Devices-87478.png
  • 2)
    Physics-Semiconductor Devices-87479.png

  • Physics-Semiconductor Devices-87480.png

  • Physics-Semiconductor Devices-87481.png
Application of a forward bias to a p-n junction
  • increases the number or donors on the n -side
  • increases the electric field in the depletion zone
  • increases the potential difference across (the depletion zone)
  • widens the depletion zone
The electrical conductivity of a semiconductor increases when electromagnetic radiation of wavelength shorter than 2480 nm, is incident on it, The band gap in (eV) for the semiconductor is
  • 1.1 eV
  • 2.5 eV
  • 0.5 eV
  • 0.7 eV
Frequency of given AC signal is 50 Hz. When it is connected to a half-wave rectifier, the number of output pulses given by rectifier within 1 s is
  • 50
  • 100
  • 25
  • 150
Identify the property which is not characteristic for a semiconductor ?
  • At a very low temperature, it behaves like an insulator
  • At higher temperatures two types of charge carriers will cause conductivity
  • The charge carriers are electrons and holes in the valence band at higher temperatures
  • The semiconductor is electrically neutral
In a p-n junction diode acting as a half-wave rectifier, which of the following statement is not true ?
  • the average output voltage over a cycle is non-zero
  • The drift current depends on biasing
  • The depletion zone decreases in forward biasing
  • The diffusion current increases due to forward biasing
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