JEE Questions for Physics Semiconductor Devices Quiz 12 - MCQExams.com

An alternating current can be converted into direct current by a
  • Dynamo
  • Motor
  • Transformer
  • Rectifier
A p-n junction diode contains a depletion layer
  • Only if it is unbiased
  • Only if it is forward biased
  • Only if it is reverse biased
  • Irrespective of whether it is biased or unbiased
Pick out the statement which is not correct
  • At a low temperature, the resistance of a semiconductor is very high
  • Movement of holes is restricted to the valence band only
  • Width of the depletion region increases as the forward bias voltage increases in case of a N — P junction diode
  • In a forward bias condition, the diode heavily conducts
Which one of the following statement is not correct in the case of light emitting diodes?
  • It is a heavily doped p-n junction
  • It emits light only when it is forward biased
  • It emits light only when it is reverse biased
  • The energy of the light emitted is less than the energy gap of the semiconductor used
In the given circuit The current through the battery is
Physics-Semiconductor Devices-87833.png
  • 0.5 A
  • 1 A
  • 1.5 A
  • 2 A
  • 2.5 A
Avalanche breakdown in a P-N junction diode is due to
  • Sudden shift to Fermi level
  • Increase in the width of forbidden gap
  • Sudden increase of impurity concentration
  • Cumulative effect of increased electron collision and creative of added electron hole pairs
In an unbiased p-n junction, holes diffuse from p-region to n-region, because
  • Free electrons in the n-region attract them
  • They move across the junction by the potential difference
  • Hole concentration in p-region is more as compared to n-region
  • All of the above
The emitter-base junction of a transistor is ... biased while the collector-base junction is ... biased
  • Reverse, forward
  • Reverse, reverse
  • Forward, forward
  • Forward, reverse
In the case of constants α and β of a transistor
  • α = β
  • β < 1, α > 1
  • α β = 1
  • β > 1, α < 1
If l1, l2, l3 are the lengths of the emitter, base and collector of a transistor, then
  • l1 = l2 = l3
  • l3 < l2 > l3
  • l3 < l1 < l2
  • l3 > l1 > l2
In an NPN transistor circuit, the collector current is 10 mA. If 90% of the electrons emitted reach the collector, the emitter current (iE) and base current (iB ) are given by
  • iE = –1 mA, iB = 9 mA
  • iE = 9 mA, iB = –1 mA
  • iE = 1 mA, iB = 11 mA
  • iE = 11 mA, iB = 1 mA
Least doped region in a transistor
  • Either emitter or collector
  • Base
  • Emitter
  • Collector
The transistors provide good power amplification when they are used in
  • Common collector configuration
  • Common emitter configuration
  • Common base configuration
  • None of the above
The transfer ratio of a transistor is 50. The input resistance of the transistor when used in the common-emitter configuration is 1 k Ω. The peak value for an A.C input voltage of 0.01 V of collector current is
  • 100 µA
  • 0.01 mA
  • 0.25 mA
  • 500 µA
For a transistor the parameter β = 99. The value of the parameter a is
  • 0.9
  • 0.99
  • 1
  • 9
In a PNP transistor the base is the N-region. Its width relative to the P-region is
  • Smaller
  • Larger
  • Same
  • Not related
A common emitter amplifier is designed with NPN transistor (α = 0.99). The input impedance is 1 k Ω and load is 10 k Ω. The voltage gain will be
  • 9.9
  • 99
  • 990
  • 9900
The symbol given in figure represents
Physics-Semiconductor Devices-87841.png
  • NPN transistor
  • PNP transistor
  • Forward biased PN junction diode
  • Reverse biased NP junction diode
The most commonly used material for making transistor is
  • Copper
  • Silicon
  • Ebonite
  • Silver
An NPN-transistor circuit is arranged as shown figure. It is
Physics-Semiconductor Devices-87843.png
  • A common base amplifier circuit
  • A common emitter amplifier circuit
  • A common collector amplifier circuit
  • Neither of the above
The part of a transistor which is heavily doped to produce a large number of majority carriers, is
  • Base
  • Emitter
  • Collector
  • None of these
For a transistor, the current amplification factor is 0.8. The transistor is connected in common emitter configuration. The change in the collector current when the base current changes by 6 mA is
  • 6 mA
  • 4.8 mA
  • 24 mA
  • 8 mA
In a common base amplifier circuit, calculate the change in base current if that in the emitter current is 2 mA and α = 0.98
  • 0.04 mA
  • 1.96 mA
  • 0.98 mA
  • 2 mA
In case of NPN-transistors the collector current is always less than the emitter current because
  • Collector side is reverse biased and emitter side is forward biased
  • After electrons are lost in the base and only remaining ones reach the collector
  • Collector side is forward biased and emitter side is reverse biased
  • Collector being reverse biased attracts less electrons
In a transistor circuit shown here the base current is 35µA. The value of the resistor Rb is
Physics-Semiconductor Devices-87847.png
  • 123.5 k Ω
  • 257 k Ω
  • 380.05 k Ω
  • None of these
In a common emitter amplifier the input signal is applied across
  • Anywhere
  • Emitter-collector
  • Collector-base
  • Base-emitter
If β, RL and r are the A.C current gain, load resistance and the input resistance of a transistor respectively in CE configuration, the voltage and the power gains respectively are

  • Physics-Semiconductor Devices-87849.png
  • 2)
    Physics-Semiconductor Devices-87850.png

  • Physics-Semiconductor Devices-87851.png

  • Physics-Semiconductor Devices-87852.png
Which of the following is used to produce radio waves of constant amplitude?
  • Oscillator
  • FET
  • Rectifier
  • Amplifier
In a common base amplifier the phase difference between the input signal voltage and the output voltage is
  • 0
  • π /4
  • π /2
  • π
NPN transistors are preferred to PNP transistors because they have
  • Low cost
  • Low dissipation energy
  • Capability of handing large power
  • Electrons having high mobility than holes
In a transistor in CE configuration, the ratio of power gain to voltage gain is
  • α
  • β / α
  • βα
  • β
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
  • 50
  • 51
  • 48
  • 49
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
The concentrations of impurities in a transistor are
  • Equal for the emitter, base and collector regions
  • Least for the emitter region
  • Largest for the emitter region
  • Largest for the base region
A working transistor with its three legs marked P, Q and R is tested using a multimeter. No conduction is found between P and Q. By connecting the common (negative) terminal of the multimeter to R and the other (positive) terminal to P or Q, some resistance is seen on the multimeter. Which of the following is true for the transistor?
  • It is a pnp transistor with R as collector
  • It is a pnp transistor with R as emitter
  • It is an npn transistor with R as collector
  • It is an npn transistor with R as base
A common emitter amplifier gives an output of 3 V for an input of 0.01 V. If β of the transistor is 100 and the input resistance is 1 k, then the collector resistance is
  • 1 k Ω
  • 3 k Ω
  • 30 k Ω
  • 30 Ω
  • 6 k Ω

Physics-Semiconductor Devices-87856.png
  • 250 kHz
  • 25 kHz
  • 2.5 kHz
  • 25 MHz
  • 2.5 MHz
In Colpitt oscillator the feedback network consists of
  • Two inductors and a capacitor
  • Two capacitors and an inductor
  • Three pairs of RC circuit
  • Three pairs of RI. circuit
In the circuit shown below, an input of 1 V is fed into the inverting input of an ideal OP-amplifier. The output signal Vout will be
Physics-Semiconductor Devices-87858.png
  • + 10 V
  • –10 V
  • 0 V
  • Infinity
A p-n junction has acceptor impurity concentration of 1017 cm–3 in the P side and donor impurity concentration of 1016cm–3 in the N side. What is the contact potential at the junction (KT = thermal energy, intrinsic carrier concentration ni = 1.4 × 1010 cm–3)?
  • (KT /e) ln (5 × 1012)
  • (KT /e) ln (2.5 × 1023)
  • (KT /e) In (1023)
  • (KT /e) ln (109)
A Zener diode has a contact potential of 1 V in the absence of biasing. It undergoes Zener breakdown for an electric field of 106 V/m at the depletion region of p-n junction. If the width of the depletion region is 2.5 µm, what should be the reverse biased potential for the Zener breakdown to occur
  • 3.5 V
  • 2.5 V
  • 1.5 V
  • 0.5 V
Bonding in a germanium crystal (semi-conductor) is
  • Metallic
  • Ionic
  • Vander Waal's type
  • Covalent
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 lengths and device temperature
For a common emitter amplifier, the audio signal voltage across the collector resistance 2 k Ω is 2 V. If the current amplification factor of the transistor is 200 and the base resistance is 1.5 k Ω, the input signal voltage and base current are
  • 0.1 V and 1µA
  • 0.15 V and 10 µA
  • 0.015 V and 1 A
  • 0.0015 V and l mA
  • 0.0075 V and 5 µA
The collector supply voltage is 6 V and the voltage drop across a resistor of 600 Ω in the collector circuit is 0.6 V, in a transistor connected in common emitter mode. If the current gain is 20, the base current is
  • 0.25 mA
  • 0.05 mA
  • 0.12 mA
  • 0.02 mA
  • 0.07 mA
n a transistor if collector current is 25 mA and base current is 1 mA, then current amplification factor α is

  • Physics-Semiconductor Devices-87865.png
  • 2)
    Physics-Semiconductor Devices-87866.png

  • Physics-Semiconductor Devices-87867.png

  • Physics-Semiconductor Devices-87868.png
Given below are symbols for some logic gates
The XOR gate and NOR gate respectively are
Physics-Semiconductor Devices-87870.png
  • I and II
  • II and III
  • III and IV
  • I and IV
The logic circuit shown below has the input waveforms ‘A’ and ‘B’ as shown. Pick out the correct output waveform
Physics-Semiconductor Devices-87871.png

  • Physics-Semiconductor Devices-87872.png
  • 2)
    Physics-Semiconductor Devices-87873.png

  • Physics-Semiconductor Devices-87874.png

  • Physics-Semiconductor Devices-87875.png
A truth table is given below. Which of the following has this type of truth table?
Physics-Semiconductor Devices-87877.png
  • XOR
  • AND
  • XNOR
  • OR
The truth table shown in figure is for
A 0 0 1 1
B 0 1 0 1
Y 1 0 0 1
  • XOR
  • AND
  • XNOR
  • OR
0:0:1


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