Pure Si at 500 K has equal number of electron ( n e ) and hole ( n h ) concentrations of 1 . 5 × 10 16 m - 3 . Doping by indium increases n h to 4 . 5 × 10 22 m - 3 . The doped semiconductor is of

p- type with electron concentration n e = 5 × 10 9 m - 3

n- type with electron concentration n e = 5 × 10 22 m - 3

p- type with electron concentration n e = 2 . 5 × 10 23 m - 3

n- type with electron concentration n e = 2 . 5 × 10 10 m - 3

Physics - Semiconductor Electronics - Quiz-2

C and Si both have same lattice structure,having 4 bonding electrons in each.However, C is insulator whereas Si is intrinsic semiconductor. This is because

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in case of C, the valence band is not completely filled at absolute zero temperature
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in case of C,the condition band is partly filled even at absolute zero temperature
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the four bonding electrons in the case of C lie in the second orbit,Whereas in the case of Si they lie in the third
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4 .the four bonding electrons in the case of C lie in the third orbit, whereas for Si they lie in the fourth orbit

The figure shows a logic circuit with two inputs A and B and the output C.The voltage wave forms across A, B and C are as given.The logic circuit gate is

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AND gate
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NAND gate
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OR gate
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NOR gate

PN-junction diode works as a insulator, if connected

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To A.C.
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In forward bias
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In reverse bias
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None of these

The reverse biasing in a PN junction diode

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Decreases the potential barrier
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Increases the potential barrier
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Increases the number of minority charge carriers
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Increases the number of majority charge carriers

The electrical resistance of depletion layer is large because:

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It has no charge carriers
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It has a large number of charge carriers
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It contains electrons as charge carriers
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It has holes as charge carriers

In the circuit given below, the value of the current is

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0 amp
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$10^{- 2}$ amp
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$10^{2}$ amp
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$10^{- 3}$ amp

Symbolic representation of four logic gates

are shown as

(i)

(ii)

(iii)

(iv)

Pick out which ones are for AND, NAND and

NOT gates, respectively.

(a) (iii), (ii)and (i)

(b) (iii), (ii) and (iv)

(d) (ii), (iii) and (iv)

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2
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3
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4
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1

If a small amount of antimony is added to germanium crystal

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the antimony becomes an acceptor atom
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there will be more free electrons than holes in the semiconductor
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its resistance is increased
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it becomes a p-type semiconductor

In forward biasing of the p-n junction

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the positive terminal of the battery is connected to n-side and the depletion region becomes thin
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the positive terminal of the battery is connected to n-side and the depletion region becomes thick
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the positive terminal of the battery is connected to p-side and the depletion region becomes thin
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the positive terminal of the battery is connected to p-side and the depletion region becomes thick

In the following figure, the diodes which are forward biased, are

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III and IV only
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I and III only
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II only
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II and IV only

Pure Si at 500 K has equal number of electron $(n_{e})$ and hole $(n_{h})$ concentrations of $1.5 \times 10^{16} m^{- 3} .$ Doping by indium increases $n_{h}$ to $4.5 \times 10^{22} m^{- 3} .$ The doped semiconductor is of

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n-type with electron concentration $n_{e} = 5 \times 10^{22} m^{- 3}$
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p-type with electron concentration $n_{e} = 2.5 \times 10^{23} m^{- 3}$
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n-type with electron concentration $n_{e} = 2.5 \times 10^{10} m^{- 3}$
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p-type with electron concentration $n_{e} = 5 \times 10^{9} m^{- 3}$

A Zener diode, having breakdown voltage equal to 15 V, is used in a voltage regulator circuit shown in the figure. The current through the diode is :

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10 mA
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15 mA
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20 mA
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5 mA

Which one of the following statement is false?

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Pure Si doped with trivalent impurities gives a p-type semiconductor
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Majority carries in a n-type semiconductor are holes
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Minority carries in a p-type semiconductor are electrons
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The resistance of intrinsic semiconductor decreases with increase of temperature

The device that can act as a complete electronic circuit is

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Junction diode
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Integrated circuit
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Junction transistor
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Zener diode

The following figure shows a logic gate circuit with two inputs A and B and the output Y. The voltage waveforms of A, B and Y are as given

The logic gate is

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$NOR$ gate
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$OR$ gate
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$AND$ gate
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$NAND$ gate

For transistor action:
a. the base, emitter and collector regions should have similar size and doping concentrations.
b. the base regions must be very thin and lightly doped.
c. the emitter-base junction is forward biased and the base-collector junction is reverse biased.
d. both the emitter-base junction as well as the base-collector junction are forward biased.
Which of the following pairs of statements is correct?

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(d) and (a)
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(a) and (b)
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(b) and (c)
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(c) and (d)

A p-n photodiode is fabricated from a semiconductor with a band gap of $2.5 eV .$ It can detect a signal of wavelength

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$6000 \overset{\circ}{A}$
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$4000 nm$
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$6000 nm$
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$4000 \overset{\circ}{A}$

The symbolic representation of four logic gates

(i) (ii)

(iii) (iv)

The logic symbols for $OR,$ $NOT$ and $NAND$ gates are respectively

(a) (iii), (iv), (ii) (b) (iv), (i), (iii)

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1
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2
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3
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4

A transistor is operated in common-emitter configuration at $V_{c} = 2 v o l t$ such that a change in the base current from 100 $μ A$ to 200 $μ A$ produces a change in the collector current from 5 mA to 10 mA. The current gain is

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75
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100
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150
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50

Sodium has body centred packing.Distance between two nearest atom is $3.7 \overset{0}{A}$ . The lattice parameter is

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6.8 $\overset{0}{A}$
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4.3 $\overset{0}{A}$
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3.0 $\overset{0}{A}$
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8.6 $\overset{0}{A}$

If the lattice parameter for a crystalline structure is $3.6 \overset{0}{A},$ then the atomic radius in fcc crystal is

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(1) $1.81 \overset{0}{A}$
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(2) $2.10 \overset{0}{A}$
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(3) $2.92 \overset{0}{A}$
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(4) $1.27 \overset{0}{A}$

The voltage gain of an amplifier with 9% negative feedback is 10. The voltage gain without feedback will be

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90
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10
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1.25
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100

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

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$10 \times 10^{14} H z$
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$5 \times 10^{14} H z$
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$1 \times 10^{14} H z$
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$20 \times 10^{14} H z$

The circuit is equivalent to

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AND gate
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NAND gate
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NOR gate
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OR gate

In the forward bias arrangement of a PN-junction diode

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The N-end is connected to the positive terminal of the battery
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The P-end is connected to the positive terminal of the battery
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The direction of current is from N-end to P-end in the diode
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The P-end is connected to the negative terminal of battery

In a PN-junction diode:

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the current in the reverse biased condition is generally very small.
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the current in the reverse biased condition is small but the forward-biased current is independent of the bias voltage.
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the reverse-biased current is strongly dependent on the applied bias voltage.
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the forward-biased current is very small in comparison to reverse-biased current.

The cut-in voltage for silicon diode is approximately

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0.2 V
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0.6 V
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1.1 V
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1.4 V

The electrical circuit used to get smooth output from a rectifier circuit is called:

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oscillator.
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filter.
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amplifier.
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logic gates.

Two PN-junctions can be connected in series by three different methods as shown in the figure. If the potential difference in the junctions is the same, then the correct connections will be

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In the circuit (1) and (2)
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In the circuit (2) and (3)
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In the circuit (1) and (3)
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Only in the circuit (1)

In the depletion region of an unbiased P-N junction diode there are

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Only electrons
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Only holes
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Both electrons and holes
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Only fixed ions

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Practice Physics Quiz Questions and Answers

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Practice Physics Quiz Questions and Answers

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