Semiconductor Devices and Logic Gates · Physics · MHT CET

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MCQ (Single Correct Answer)

1

Which of the following logic gates is called as Universal gate?

MHT CET 2025 21st April Morning Shift
2

Which graph shows correctly the temperature (T). dependence of resistivity $(\rho)$ of a semiconductor?

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3

In an n-p-n transistor amplifier, the collector current is 8 mA . If $80 \%$ of the electrons from the emitter reach the collector, then ( $\alpha$ and $\beta$ are current ratios)

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4

In an n-p-n transistor amplifier, the collector current is 9 mA . If $90 \%$ of the electrons emitted reach the collector, then

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5

The resultant logic gate from the combination of following gates is

MHT CET 2025 20th April Evening Shift Physics - Semiconductor Devices and Logic Gates Question 1 English
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6

In the following circuit shown in figure, three diodes are connected each with forward resistance $40 \Omega$ and infinite backward resistance. The current through $100 \Omega$ resistance is

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7

For an ideal diode, in forward and reverse biased condition the resistance is respectively

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8

When an n-p-n junction transistor is used as an amplifier in common emitter mode,

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9

In a transistor (common emitter configuration) the ratio of power gain to voltage gain is ( $\alpha$ and $\beta$ are current ratios)

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10

In a given logic circuit, the output Y when all the three inputs $\mathrm{A}, \mathrm{B}, \mathrm{C}$ are first low and then high will be respectively

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11

In unbiased p-n junction diode

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12

In a transistor amplifier, AC current gain is 64 , the load resistance is $5400 \Omega$ and the input resistance of the transistor is $540 \Omega$. The voltage gain is

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13
In the depletion layer of reverse biased p-n junction, the
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14
For a common emitter transistor, if $\frac{I_{\mathrm{C}}}{I_{\mathrm{E}}}=0.95$, then the current gain is
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15
In the case of constant ' $\alpha$ ' and ' $\beta$ ' of a transistor ( $\alpha$ and $\beta$ are current ratios)
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16

To get the truth table shown from the following logic circuit, the logic gate G should be

MHT CET 2024 16th May Evening Shift Physics - Semiconductor Devices and Logic Gates Question 13 English

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17

The Boolean expression for the given combination of logic gates is

MHT CET 2024 16th May Evening Shift Physics - Semiconductor Devices and Logic Gates Question 14 English

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18

When a small amount of impurity atoms are added to semiconductor, then generally its resistivity

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19

The input signal given to C.E. amplifier having a voltage gain of 126 is $V_i=2 \cos \left(12 t+\frac{\pi}{3}\right)$. The corresponding output signal will be

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20

The truth table of the following circuit is

MHT CET 2024 16th May Morning Shift Physics - Semiconductor Devices and Logic Gates Question 16 English

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21

If the $\mathrm{p}-\mathrm{n}$ junction diode is unbiased,

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22

For detecting light intensity we use

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23

What is the current in the following junction diode circuit?

MHT CET 2024 15th May Evening Shift Physics - Semiconductor Devices and Logic Gates Question 19 English

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24

A p-n junction diode as a rectifier converts

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25

Two different logic gates giving output ' 1 ' for the inputs $(1,0)$ and then for $(0,1)$ are

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26

In an extrinsic n-type semiconductor, the free electrons donated by the impurity atoms occupy energy levels in

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27

For a transistor, current gain $(\beta)=50$. To change the collector current by $350 \mu \mathrm{~A}$, the base current should be changed by

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28

When n-p-n junction transistor is used as an amplifier in common emitter mode,

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29

Assuming that junction diode is ideal, the current in arrangement shown in figure

MHT CET 2024 11th May Evening Shift Physics - Semiconductor Devices and Logic Gates Question 22 English

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30

For the following digital logic circuit, the correct truth-table is

MHT CET 2024 11th May Evening Shift Physics - Semiconductor Devices and Logic Gates Question 23 English

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31

Following combination of gates is equivalent to

MHT CET 2024 11th May Morning Shift Physics - Semiconductor Devices and Logic Gates Question 30 English

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32

If ' $\mathrm{n}_{\mathrm{c}}$ ' and ' $\mathrm{n}_{\mathrm{h}}$ ' are the number of electrons and number of holes respectively in a semiconductor heavily doped with phosphorous then

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33

A p-n junction diode cannot be used

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34

In semiconductors at room temperature,

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35

In the given circuit, Zener breakdown voltage is 8 V . If power of Zener diode is 1.6 W . The value of $R$ is

MHT CET 2024 10th May Evening Shift Physics - Semiconductor Devices and Logic Gates Question 32 English

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36

The logic gate represented by following logic circuit is

MHT CET 2024 10th May Evening Shift Physics - Semiconductor Devices and Logic Gates Question 29 English

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37

Two ideal diodes are connected to a battery as shown in the circuit. The current supplied by the battery is

MHT CET 2024 10th May Morning Shift Physics - Semiconductor Devices and Logic Gates Question 35 English

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38

What is the output Y in the following circuit, when all the three inputs A, B, C are first 'zero' and then 'one'?

MHT CET 2024 10th May Morning Shift Physics - Semiconductor Devices and Logic Gates Question 34 English

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39

In the block diagram of simple rectifier circuit, from a variable a.c. voltage, constant d.c. voltage is obtained. The correct order of operation is

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40

In the working of photodiode, the reverse current depends on

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41

The resultant gate and its Boolean expression in the given circuit is

MHT CET 2024 9th May Evening Shift Physics - Semiconductor Devices and Logic Gates Question 37 English

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42

The current amplification factor of a transistor is 50 . The input resistance when used in common emitter mode is $1 \mathrm{k} \Omega$. The peak value for an a.c. input voltage of 0.01 V peak is

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43

In the logic circuit diagram, when all the four inputs $\mathrm{A}, \mathrm{B}, \mathrm{C}, \mathrm{D}$ are one, the outputs $\mathrm{Y}_1, \mathrm{Y}_2, \mathrm{Y}_3$ are respectively $(1,1,0)$. When all the inputs $\mathrm{A}, \mathrm{B}, \mathrm{C}, \mathrm{D}$ are changed to 'zero', the outputs $\mathrm{Y}_1, \mathrm{Y}_2, \mathrm{Y}_3$ respectively change to

MHT CET 2024 9th May Morning Shift Physics - Semiconductor Devices and Logic Gates Question 40 English

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44

For the diagram shown, the resistance between points A and B when the ideal diode ' $D$ ' is forward biased is ' $R_1$ ' and that when reverse biased is ' $R_2$ '. The ratio $\frac{R_1}{R_2}$ is

MHT CET 2024 9th May Morning Shift Physics - Semiconductor Devices and Logic Gates Question 39 English

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45

The truth table for the given logic circuit is

MHT CET 2024 4th May Evening Shift Physics - Semiconductor Devices and Logic Gates Question 43 English

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46

In the circuit diagram shown in figure, the current through the zener diode is

MHT CET 2024 4th May Evening Shift Physics - Semiconductor Devices and Logic Gates Question 42 English

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47

The depletion layer in p-n junction region is caused by

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48

The collector supply voltage is 6 V and a voltage drop across a resistor of $600 \Omega$ in the collector circuit is 0.6 V , in a circuit of transistor connected in common emitter mode. If the current gain is 20 then the base current is

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49

A zener diode, having breakdown voltage 15 V is used in a voltage regulator circuit as shown. The current through the zener diode is

MHT CET 2024 4th May Morning Shift Physics - Semiconductor Devices and Logic Gates Question 45 English

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50

A semiconductor device X is connected in series with a battery and a resistor. The current of 10 mA is found to pass through the circuit. If the terminals of X are connected in reverse manner, the current drops to almost zero. X may be

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51

The Boolean expression for ' $x-O R$ ' gate $C=(A \oplus B)$ is equal to

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52

Which one of the following statements is true? A p-type semiconductor is doped with

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53

The combination of NAND gates is shown in figure (I) and (II). For the given inputs, the outputs in both the combinations are respectively.

MHT CET 2024 3rd May Evening Shift Physics - Semiconductor Devices and Logic Gates Question 48 English

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54

An n-p-n transistor can be considered to be equivalent to two diodes connected. The correct figure out of the following is

MHT CET 2024 3rd May Morning Shift Physics - Semiconductor Devices and Logic Gates Question 52 English

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55

Find the magnitude of current in the given circuit.

MHT CET 2024 3rd May Morning Shift Physics - Semiconductor Devices and Logic Gates Question 51 English

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56

In common emitter transistor amplifier, load resistance is $6.5 \mathrm{k} \Omega$ and an input resistance is $1.3 \mathrm{k} \Omega$. If the current gain is 78 , the voltage gain is

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57

The potential barrier in p-n junction diode is due to

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58

The logic gate combination circuit shown in the figure performs the logic function of

MHT CET 2024 2nd May Evening Shift Physics - Semiconductor Devices and Logic Gates Question 54 English

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59

In semiconductors at room temperature,

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60

The logic circuit in figure is equivalent to

MHT CET 2024 2nd May Morning Shift Physics - Semiconductor Devices and Logic Gates Question 56 English

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61

In an NPN transistor $10^{10}$ electrons enter the emitter in $10^{-6} \mathrm{~s}$ and $2 \%$ electrons recombine with holes in base. The current ratios ' $\alpha$ ' and ' $\beta$ ' of a transistor are respectively (nearly)

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62

The output of following combination is same as that of

MHT CET 2023 14th May Evening Shift Physics - Semiconductor Devices and Logic Gates Question 90 English

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63

In an n-p-n transistor, the collector current is $$28 \mathrm{~mA}$$. If $$80 \%$$ of electrons reach the collector, its base current in $$\mathrm{mA}$$ is

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64

When the conductivity of a semiconductor is only due to the breaking of the covalent bonds, the semiconductor is called

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65

For a common emitter configuration, if '$$\alpha$$' and '$$\beta$$' have their usual meanings, the incorrect relation between '$$\alpha$$' and '$$\beta$$' is

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66

For emission of light, a light emitting diode (LED) is

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67

In semiconductors at room temperature,

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68

The Boolean expression for the following combination is

MHT CET 2023 13th May Evening Shift Physics - Semiconductor Devices and Logic Gates Question 94 English

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69

If the maximum efficiency of a full wave rectifier is $$x \%$$ and that of half-wave rectifier is $$y \%$$, then the relation between $$x$$ and $$y$$ is

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70

Doping of a semiconductor (with small impurity atoms) generally changes the resistivity as follows.

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71

The following graph represents

MHT CET 2023 13th May Morning Shift Physics - Semiconductor Devices and Logic Gates Question 99 English
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72

If two inputs of a NAND gate are shorted, the resulting gate is

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73

On increasing the reverse bias to a large value in a P-N junction diode, current

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74

In the following digital logic circuit, the output Y will be '1' for inputs

MHT CET 2023 12th May Evening Shift Physics - Semiconductor Devices and Logic Gates Question 105 English

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75

Which one of the following statements is WRONG regarding LED?

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76

In which figure, the junction diode is forward biased?

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77

The following logic gate combination is equivalent to

MHT CET 2023 12th May Morning Shift Physics - Semiconductor Devices and Logic Gates Question 104 English

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78

The logic gate combination circuit shown in the figure performs the logic function of

MHT CET 2023 12th May Morning Shift Physics - Semiconductor Devices and Logic Gates Question 103 English

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79

When forward bias is applied to a p-n junction, then what happens to the potential barrier $$\left(V_B\right)$$ and the width $$(\mathrm{X})$$ of the depletion region?

MHT CET 2023 12th May Morning Shift
80

In the study of transistor as an amplifier if $$\alpha=\frac{I_C}{I_E}=0.98$$ and $$\beta=\frac{I_C}{I_B}=49$$, where $$I_C, I_B$$ and $$\mathrm{I}_{\mathrm{E}}$$ are collector, base and emitter current respectively then $$\left(\frac{1}{\alpha}-\frac{1}{\beta}\right)$$ is equal to

MHT CET 2023 11th May Evening Shift
81

If $$p$$-$$n$$ junction diode is in forward bias then

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82

In the digital circuit the inputs are as shown in figure. The Boolean expression for output $$\mathrm{Y}$$ is

MHT CET 2023 11th May Evening Shift Physics - Semiconductor Devices and Logic Gates Question 106 English

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83

Identify the correct circuit diagrams for the normal operation from the following.

MHT CET 2023 11th May Morning Shift Physics - Semiconductor Devices and Logic Gates Question 109 English

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84

In energy band diagram of insulators, a band gap and the conduction band is respectively

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85

In the case of NAND gate, if A and B are the inputs and $$\mathrm{Y}$$ is the output then

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86

A pure $$\mathrm{Si}$$ crystal has $$4 \times 10^{28}$$ atoms per $$\mathrm{m}^3$$. It is doped by 1 ppm concentration of antimony. The number of free electrons available will be

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87

The output of an 'OR' gate is connected to both the inputs of a 'NAND' gate. The combination will serve as

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88

Which one of the operations of $$\mathrm{n}-\mathrm{p}-\mathrm{n}$$ transistor differs from that of $$p-n-p$$ transistor?

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89

For the diagram shown, the resistances between points A and B when ideal diode D is forward biased is '$$R_1$$' and that when reverse biased is '$$R_2$$'. The ratio $$R_1: R_2$$ is

MHT CET 2023 10th May Evening Shift Physics - Semiconductor Devices and Logic Gates Question 112 English

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90

To obtain the truth-table shown, from the following logic circuit, the gate G should be

MHT CET 2023 10th May Morning Shift Physics - Semiconductor Devices and Logic Gates Question 110 English

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91

In insulators

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92

Identify the mismatch out of the following.

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93

In the reverse biasing of a p-n junction diode :

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94

In a transistor, in common emitter configuration, the ratio of power gain to voltage gain is

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95

If the frequency of the input voltage is $$50 \mathrm{~Hz}$$, applied to a (a) half wave rectifier and (b) full wave rectifier. The output frequency in both cases is respectively

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96

For an intrinsic semiconductor $$\left(\mathrm{n}_{\mathrm{h}}\right.$$ and $$\mathrm{n}_{\mathrm{e}}$$ are the number of holes per unit volume and number of electrons per unit volume respectively)

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97

A $$5.0 \mathrm{~V}$$ stabilized power supply is required to be designed using a $$12 \mathrm{~V}$$ DC power supply as input source. The maximum power rating of zener diode is $$2.0 \mathrm{~W}$$. The minimum value of resistance $$R_{\mathrm{s}}$$ in $$\Omega$$ connected in series with zener diode will be

MHT CET 2023 9th May Morning Shift
98

To get the truth table shown, from the following logic circuit, the Gate G should be

MHT CET 2023 9th May Morning Shift Physics - Semiconductor Devices and Logic Gates Question 124 English

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99

For a NAND gate, the inputs and outputs are given below.

Input A Input B Output Y
0 1 $$\mathrm{C}$$
0 0 $$\mathrm{D}$$
1 0 $$\mathrm{E}$$
1 1 $$\mathrm{F}$$

The values taken by C, D, E, F are respectively

MHT CET 2022 11th August Evening Shift
100

The given circuit has two ideal diodes $$D_1$$ and $$D_2$$ connected as shown in the figure. The current flowing through the resistance $$R_1$$ will be

MHT CET 2022 11th August Evening Shift Physics - Semiconductor Devices and Logic Gates Question 86 English

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101

Choose the correct statement. In conductors

MHT CET 2021 24th September Evening Shift
102

For a transistor, the current ratio $$\alpha_{\mathrm{dc}}=\frac{69}{70}$$, the current gain $$\beta_{\mathrm{dc}}$$ is

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103

The input a.c. voltage of frequency $$60 \mathrm{~Hz}$$ is applied to half-wave rectifier and also to full-wave rectifier. The output frequency in case of half-wave rectifier and that in case of full wave rectifier is respectively.

MHT CET 2021 24th September Evening Shift
104

A p-n junction photodiode is fabricated from a semiconductor with a band gap of $$2.5 \mathrm{~eV}$$. It can detect a signal of wavelength [Planck's constant $$=6.6 \times 10^{-34} \mathrm{Js}, \mathrm{c}=3 \times 10^8 \mathrm{~m} / \mathrm{s}, \mathrm{e}=1.6 \times 10^{-19} \mathrm{C}$$]

MHT CET 2021 24th September Morning Shift
105

For the output of the following logic circuit to be 'I', the values of inputs A and B should be respectively

MHT CET 2021 24th September Morning Shift Physics - Semiconductor Devices and Logic Gates Question 73 English

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106

Two identical ideal diodes are connected to an ammeter and a d.c source (1 volt) as shown. In which one of the following circuits, ammeter will not show any deflection?

MHT CET 2021 24th September Morning Shift Physics - Semiconductor Devices and Logic Gates Question 72 English

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107

When the temperature of a semiconductor is increased, its resistance and electric conductivity respectively.

MHT CET 2021 23rd September Evening Shift
108

For a two input AND gate, the four entries are shown in the truth table. Identify the correct ones out of these $$(\mathrm{A}, \mathrm{B}=$$ input, $$\mathrm{Y}=$$ output)

Entry A B Y
1 0 1 0
2 1 0 0
3 1 1 1
4 0 0 1

MHT CET 2021 23rd September Evening Shift
109

In a CE transistor, a change of $$8.0 \mathrm{~mA}$$ in the emitter current produces a change of $$7.8 \mathrm{~mA}$$ in the collector current. What change in the base current is necessary to produce the same change in the collector current?

MHT CET 2021 23rd September Evening Shift
110

The resultant gate and its Boolean expression in the given circuit is

MHT CET 2021 23th September Morning Shift Physics - Semiconductor Devices and Logic Gates Question 78 English

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111

What are the values of the currents flowing in each of the following diode circuits $$\mathrm{X}$$ and $$\mathrm{Y}$$ respectively? (Assume that the diodes are ideal)

MHT CET 2021 23th September Morning Shift Physics - Semiconductor Devices and Logic Gates Question 79 English

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112

In common emitter amplifier, a change of 0.2 mA in the base current causes a change of 5 mA in the collector current. If input resistance is 2 k$$\Omega$$ and voltage gain is 75, the load resistance used in the circuit is

MHT CET 2021 23th September Morning Shift
113

Which of the following gates will give an output '1' for the given inputs?

MHT CET 2021 22th September Evening Shift Physics - Semiconductor Devices and Logic Gates Question 83 English

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114

For a common-emitter amplifier, the voltage gain is 40. Its input and output impedances are $$100 \Omega$$ and $$400 \Omega$$, respectively. The power gain of the CE amplifier will be

MHT CET 2021 22th September Evening Shift
115

Choose the correct statement. In semiconductors valance band and conduction band

MHT CET 2021 22th September Evening Shift
116

A logic gate which gives output 'HIGH' only when its two input terminals are at different logic levels with respect to each other is

MHT CET 2021 22th September Morning Shift
117

Choose the FALSE statement from the following.

MHT CET 2021 22th September Morning Shift
118

In an n-p-n transistor 200 electrons enter the emitter in 10$$^{-8}$$ second. If 1% electrons are lost in the base, then the current that enters the emitter and the current amplification factor are respectively [e = 1.6 $$\times$$ 10$$^{-19}$$ C]

MHT CET 2021 22th September Morning Shift
119

Combination of NAND gates is shown in the figure. It is equivalent to

MHT CET 2021 21th September Evening Shift Physics - Semiconductor Devices and Logic Gates Question 130 English

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120

In an ideal junction diode, the current flowing through PQ is

MHT CET 2021 21th September Evening Shift Physics - Semiconductor Devices and Logic Gates Question 128 English

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121

LED is manufactured using zinc selenide then it emits.

MHT CET 2021 21th September Evening Shift
122

In a pure silicon, number of electrons and holes per unit volume are $$1.6 \times 10^{16} \mathrm{~m}^{-3}$$. If silicon is doped with Boron in a way that on doping hole density increases to $$4 \times 10^{22} \mathrm{~m}^{-3}$$. Then electron density in doped semiconductor will be

MHT CET 2021 21th September Morning Shift
123

For a transitor, $$\frac{1}{\alpha_{\mathrm{DC}}}-\frac{1}{\beta_{\mathrm{DC}}}$$ is equal to [ $$\alpha_{\mathrm{DC}}$$ and $$\beta_{\mathrm{DC}}$$ are current amplification factors]

MHT CET 2021 21th September Morning Shift
124

The current in the following circuit is

MHT CET 2021 21th September Morning Shift Physics - Semiconductor Devices and Logic Gates Question 132 English

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125

The output of an 'OR' gate is 'one'

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126

In the case of insulators, a band gap and conduction band is respectively

MHT CET 2021 20th September Evening Shift
127

A rectifier is used to

MHT CET 2021 20th September Evening Shift
128

Two different logic gates moving output '0' for the inputs (0, 1) and then for (1, 0) are

MHT CET 2021 20th September Morning Shift
129

The frequency of a given a.c. signal is 'N' Hz. When it is connected to a half wave rectifier, the number of output pulses given by the rectifier in 1 second is

MHT CET 2021 20th September Morning Shift
130

Silicon and copper are cooled from 300 K to 100 K, the specific resistance (resistivity)

MHT CET 2021 20th September Morning Shift
131

A transistor having $\alpha=0.8$ is connected in common emitter configuration. When the base current changes by 6 mA , then the change in collector current is

MHT CET 2020 19th October Evening Shift
132

In an intrinsic semiconductor, at an ordinary temperature, the correct relation between the number of electrons per unit volume $n_e$ and number of holes per unit volume $n_h$.

MHT CET 2020 19th October Evening Shift
133

$$A$$ transistor has a voltage gain $$A$$. If the amount $$\beta A$$ of its output is applied to the input of the transistor, then the transistor becomes oscillator, when

MHT CET 2020 16th October Evening Shift
134

At absolute zero temperature, pure silicon behaves as

MHT CET 2020 16th October Evening Shift
135

In common emitter amplifier, input resistance is $$1000 \Omega$$, peak value of input signal voltage is $$5 \mathrm{~mV}$$ and $$\beta=60$$. The peak value of output current is

MHT CET 2020 16th October Morning Shift
136

When a small amount of impurity atoms are added to a semiconductor, then generally its resistivity

MHT CET 2020 16th October Morning Shift
137

$V-I$ characterstics of LED is shown correctly by graph

MHT CET 2019 3rd May Morning Shift
138

Which of the following regions of a transistors are, respectively, heavily dopped and lightly dopped?

MHT CET 2019 3rd May Morning Shift
139

In case of $p$-n junction diode, the width of depletion region is

MHT CET 2019 2nd May Evening Shift
140

In the study of transistor as an amplifier, the ratio of collector current to emitter current is 0.98 then the ratio of collector current to base current will be

MHT CET 2019 2nd May Evening Shift
141

Assuming that the junction diode is ideal, the current in the arrangement shown in figure is

MHT CET 2019 2nd May Morning Shift Physics - Semiconductor Devices and Logic Gates Question 63 English

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142

. For a transistor, the current ratio ' $\beta_{d c}$ ' is defined as the ratio of

MHT CET 2019 2nd May Morning Shift
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