JEE Questions for Physics Semiconductor Devices Quiz 1 - MCQExams.com

In order to rectify an alternating current one uses a
  • thermo couple
  • diode
  • triode
  • transistor
To obtain OR gate from NOR gate, you will need ____________
  • One NOR gate
  • One NOT gate
  • Two NOT gate
  • One OR gate
In CE mode, the input characteristics of a transistor is the variation of
  • IB against VBE at constant VCE
  • IC against VCE at constant VBE
  • IB against IC
  • IE against IC
In a transistor the collector current is always less than the emitter current because
  • collector side is reverse biased and the emitter side is forward biased
  • a few electrons are lost in the base and only remaining ones reach the collector
  • collector being reverse biased, attracts less electrons
  • collector side is forward biased and emitter side is reverse biased
When n-p-n transistor is used as an amplifier,
  • electrons move from emitter to base
  • electrons move from base to emitter
  • electrons move from collector to base
  • holes move from base to emitter
The correct relation between α and β in a transistor is

  • Physics-Semiconductor Devices-87422.png
  • 2)
    Physics-Semiconductor Devices-87423.png

  • Physics-Semiconductor Devices-87424.png

  • Physics-Semiconductor Devices-87425.png
When p-n junction is forward biased
  • depletion layer reduces and barrier height increases
  • depletion layer widen and barrier height reduces
  • both (and (2)
  • depletion layer and barrier height increases
The phase difference between input and output voltages of a CE circuit is
  • 0°
  • 90°
  • 180°
  • 270°
An oscillator is nothing but an amplifier with
  • Positive feed back
  • Large gain
  • No feedback
  • Negative feedback
For a given plate-voltage, the plate current in a triode is maximum when the potential of
  • The grid is positive and plate is negative
  • The grid is positive and plate is positive
  • The grid is zero and plate is positive
  • The grid is negative and plate is positive
The energy gap of silicon is 1.5 eV. At what wavelength the silicon will stop to absorb the photon?
  • 8250 Å
  • 7250 Å
  • 6875.5 Å
  • 5000 Å
In a common-base mode of a transistor, the collector current is 5.488 mA for an emitter current of 5.60 mA. The value of the base current amplification factor ( β ) will be
  • 49
  • 50
  • 51
  • 48
The part of a transistor which is heavily doped to produce a large number of majority carriers is
  • base
  • emitter
  • collector
  • None of these
In a common-base amplifier, the phase difference between the input signal voltage and output voltage is
  • π / 4
  • π
  • zero
  • π / 2
The forward biased diode connection is

  • Physics-Semiconductor Devices-87382.png
  • 2)
    Physics-Semiconductor Devices-87383.png

  • Physics-Semiconductor Devices-87384.png

  • Physics-Semiconductor Devices-87385.png
In a semiconductor, separation between conduction and valence band is of the order of
  • 0 eV
  • 1 eV
  • 10 eV
  • 50 eV
In the bandgap between valence hand and conduction band in a material is 5.0 eV, then the material is
  • semiconductor
  • good conductor
  • superconductor
  • insulator
The energy band gap (distance between the conduction band and valence band) in conductor is
  • zero
  • 4 Å
  • 10 Å
  • 100 Å
For an insulator, the forbidden energy gap is
  • zero
  • 1 eV
  • 5 eV
  • 2 eV
When a solid with a band gap has a donor level just below its empty energy band, the solid is
  • a conductor
  • an insulator
  • p–type semiconductor
  • n–type semiconductor
A solid reflects incident light and its electrical conductivity decreases with temperature. The binding in this solid is
  • ionic
  • covalent
  • metallic
  • molecular
In a cubic unit cell of bcc structure, the lattice points (i.e. number of atoms) are
  • 2
  • 6
  • 8
  • 12
  • 5
Copper has face centred cubic (fcc) lattice with interatomic spacing equal to 2.54 Å. The value of lattice constant for this lattice is
  • 1.27 Å
  • 5.08 Å
  • 2.54 Å
  • 3.59 Å
The ionic bond is absent in
  • NaCl
  • CsCl
  • LiF
  • H2O
If α-current gain of a transistor is 0.98. What is the value of β-current gain of the transistor?
  • 0.49
  • 49
  • 4.9
  • 5
In a common-emitter amplifier, the load resistance of the output circuit is 1000 times the resistance of the input circuit. If α = 0.98, then voltage gain is
  • 49 × 103
  • 2.5 × 102
  • 1.5 × 102
  • 4.9
In a common emitter–amplifier, the input signal is applied across
  • anywhere
  • emitter–collector
  • collector–base
  • base–emitter
An n-p-n transistor can be considered to be equivalent to two diodes, connected. Which of the following figures is the correct one?

  • Physics-Semiconductor Devices-87374.png
  • 2)
    Physics-Semiconductor Devices-87375.png

  • Physics-Semiconductor Devices-87376.png

  • Physics-Semiconductor Devices-87377.png
The current gain of a common-base transistor circuit is 0.96. On changing the emitter current by 10.0 mA, the change in the base current will be
  • 9.6 mA
  • 0.4 mA
  • 19.6 mA
  • 24 mA
In a common-emitter amplifier the input signal is applied across the
  • anywhere
  • emitter–collector
  • collector–base
  • base–emitter
In a common emitter transistor amplifier, the output resistance is 500 kΩ and the current gain β = 49. If the power gain of the amplifier is 5 × 106, the input resistance is
  • 325 Ω
  • 165 Ω
  • 198 Ω
  • 225 Ω
  • 240 Ω
In a transistor the base is
  • an insulator
  • a conductor of low resistance
  • a conductor of high resistance
  • an extrinsic semiconductor
In BJT, maximum current flows in which of the following?
  • Emitter region
  • Base region
  • Collector region
  • Equal in all the regions
A change of 8.0 mA in the emitter current brings a change of 7.9 mA in the collector current. The values of α and β are
  • 0.99, 90
  • 0.96, 79
  • 0.97, 99
  • 0.99, 79
An amplifier has a voltage gain AV =1000. The voltage gain in dB is
  • 30 dB
  • 60 dB
  • 3 dB
  • 20 dB
A common emitter amplifier has a voltage gain of 50, an input impedance of 100 Ω , and an output impedance of 200 Ω . The power gain of the amplifier is
  • 500
  • 1000
  • 1250
  • 100
When the conductivity of a semiconductor is only due to breaking of covalent bonds, the semiconductor is called
  • intrinsic
  • extrinsic
  • p–type
  • n–type
LED is a p-n junction diode which is
  • forward biased
  • either forward biased or reverse biased
  • reverse biased
  • neither forward biased nor reverse biased
Electric conduction in semi-conductor takes place due to
  • electrons only
  • holes only
  • both electrons and holes
  • None of the above
Name of a p-n junction, which can be used as the regulator, is
  • zener diode
  • tunnel diode
  • gunn diode
  • None of these
A zener diode is used for
  • rectification
  • modulation
  • detection
  • voltage regulation
In LED visible light is produced by
  • gallium phosphide
  • gallium arsenide
  • germanium phosphide
  • silicon phosphide
The temperature coefficient of a zener mechanism is
  • negative
  • positive
  • infinity
  • zero
In a diode, when there is a saturation current, the plate resistance will be
  • data insufficient
  • zero
  • some finite quantity
  • infinite quantity
If a full wave rectifier circuit is operating from 50Hz mains, the fundamental frequency in the ripple will be
  • 70.7 Hz
  • 100 Hz
  • 25 Hz
  • 59 Hz
Barrier potential of a p-n junction diode does not depend on
  • forward bias
  • doping density
  • diode design
  • temperature
When the forward bias voltage of a diode is changed from 0.6 V to 0.7 V, the current changes from 5 mA to 15 mA. Then its forward bias resistance is
  • 0.01Ω
  • 0.1Ω
  • 10Ω
  • 100Ω
  • 0.2Ω
The potential in depletion layer is due to
  • electrons
  • holes
  • ions
  • forbidden band
In breakdown region, a zener diode behaves as a
  • constant current source
  • constant voltage source
  • constant resistance source
  • constant power source
When boron is added as an impurity to silicon, the resulting material is
  • n -type semiconductor
  • n -type conductor
  • p-type conductor
  • p-type semiconductor
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