NEET-UG SERIES
Physics

Semiconductor Electronics Materials Devices And Simple Circuits

73 previous year questions.

Volume: 73 Ques
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Chapter Questions
73 MCQs

01
PYQ 1988
medium
physics ID: neet-ug-
p-n junction is said to be forward biased, when
1
the positive pole of the battery is joined to the p-semiconductor and negative pole to the n-semiconductor
2
the positive pole of the battery is joined to the n-semiconductor and p -semiconductor
3
the positive pole of the battery is connected to n-semiconductor and p-semiconductor
4
a mechanical force is applied in the forward direction.
02
PYQ 1988
medium
physics ID: neet-ug-
At absolute zero, Si acts as
1
non metal
2
metal
3
insulator
4
none of these.
03
PYQ 1992
medium
physics ID: neet-ug-
A piece of copper and other of germanium are cooled from the room temperature to 80 K, then
1
resistance of each will increase
2
resistance of copper will decrease
3
the resistance of copper will increase while that of germanium will decrease
4
the resistance of copper will decrease while that of germanium will increase
04
PYQ 1993
medium
physics ID: neet-ug-
Diamond is very hard because
1
it is covalent solid
2
it has large cohesive energy
3
high melting point
4
insoluble in all solvents
05
PYQ 1996
medium
physics ID: neet-ug-
When npn transistor is used as an amplifier, then
1
electrons move from collector to base
2
holes move from base to emitter
3
electrons move from base to collector
4
electrons move from emitter to base.
06
PYQ 1997
medium
physics ID: neet-ug-
To obtain a -type germanium semiconductor, it must be doped with
1
indium
2
phosphorus
3
arsenic
4
antimony.
07
PYQ 1998
medium
physics ID: neet-ug-
A semiconducting device is connected in a series circuit with a battery and a resistance. A current is found to pass through the circuit. If the polarity of the battery is reversed, the current drops to almost zero. The device may be
1
a type semiconductor
2
an intrinsic semiconductor
3
a junction
4
an type semiconductor
08
PYQ 1999
medium
physics ID: neet-ug-
Depletion layer consists of
1
mobile ions
2
protons
3
electrons
4
immobile ions
09
PYQ 1999
medium
physics ID: neet-ug-
A p-n junction diode can be used as
1
condenser
2
regulator
3
amplifier
4
rectifier
10
PYQ 2000
medium
physics ID: neet-ug-
From the following diode circuit. Which diode in forward biased condition:
1

Which diode in forward biased condition

2

Which diode in forward biased condition

3

Which diode in forward biased condition

4

Which diode in forward biased condition

11
PYQ 2000
medium
physics ID: neet-ug-
Given truth table is correct for:
ABY
111
100
010
000
1
NAND
2
AND
3
NOR
4
OR
12
PYQ 2001
hard
physics ID: neet-ug-
For a common emitter circuit if then current gain for common emitter circuit will be
1
49
2
98
3
4.9
4
25.5
13
PYQ 2001
medium
physics ID: neet-ug-

Following truth table represent which logic gate -

ABC
110
011
101
001
1

XOR

2

NOT

3

NAND

4

AND

14
PYQ 2001
medium
physics ID: neet-ug-

The current (I) in the circuit will be : -
 

current (I) in the circuit
1

2

3

4

15
PYQ 2002
medium
physics ID: neet-ug-

For a transistor = 0.96, then the current gain for the common emitter configuration

1
12
2
6
3
48
4
24
16
PYQ 2002
medium
physics ID: neet-ug-

In a PN junction :

1

High potential at N side and low potential at P side

2

High potential at P side and low potential at N side

3

P and N both are at same potential

4

Undetermined

17
PYQ 2002
medium
physics ID: neet-ug-

The given truth table is for which logic gate : 

truth table

1

NAND

2

XOR

3

NOR

4

OR

18
PYQ 2002
medium
physics ID: neet-ug-
For the given circuit of p-n junction diode which is correct :-
1
in forward bias the voltage across R is V
2
in reverse bias the voltage across R is V
3
in forward bias the voltage across R is 2V
4
in reverse bias the voltage across R is 2V.
19
PYQ 2003
medium
physics ID: neet-ug-
Barrier potential of a p-n junction diode does not depend on:
1
diode design
2
temperature
3
forward bias
4
doping density
20
PYQ 2003
medium
physics ID: neet-ug-
If a full wave rectifier circuit is operating from 50 Hz mains, the fundamental frequency in the ripple will be:
1
25 Hz
2
50 Hz
3
70.7 Hz
4
100 Hz
21
PYQ 2003
medium
physics ID: neet-ug-
A n-p-n transistor conducts when
1
both collector and emitter are positive with respect to the base
2
collector is positive and emitter is negative with respect to the base
3
collector is positive and emitter is at same potential as the base
4
both collector and emitter are negative with respect to the base
22
PYQ 2003
medium
physics ID: neet-ug-
Reverse bias applied to a junction diode
1
Lowers the potential barrier
2
raises the potential barrier
3
increases the majority carrier current
4
increases the minority carrier current
23
PYQ 2003
medium
physics ID: neet-ug-
transistor conducts when
1
both collector and emitter are positive with respect to the base
2
collector is positive and emitter is negative with respect to the base
3
collector is positive and emitter is at same potential as the base
4
both collector and emitter are negative with respect to the base
24
PYQ 2003
medium
physics ID: neet-ug-
Following diagram performs the logic function of:
logic function
1

AND gate

2

NAND gate

3

OR gate

4

XOR gate

25
PYQ 2004
medium
physics ID: neet-ug-
The output of OR gate is 1
1

If either or both inputs are 1

2

Only if both inputs are 1

3

If either input is zero

4

if both inputs are zero

26
PYQ 2004
medium
physics ID: neet-ug-
In a p–n junction photocell, the value of the photo electromotive force produced by monochromatic light is proportional to
1

The intensity of the light falling on the cell

2

The frequency of the light falling on the cell

3

The voltage applied at the p–n junction

4

The barrier voltage at the p–n junction

27
PYQ 2004
medium
physics ID: neet-ug-
The peak voltage in the output of a half-wave diode rectifier fed with a sinusoidal signal without a filter is 10V. The d. c. component of the output voltage is
1

V

2

10 V

3

V

4

V

28
PYQ 2004
medium
physics ID: neet-ug-
In semiconductors at a room temperature
1

The valence band is completely filled and the conduction band is partially filled

2

The valence band is completely filled

3

The conduction band is completely empty

4

The valence band is partially empty and the conduction band is partially filled

29
PYQ 2004
easy
physics ID: neet-ug-
Of the diodes shown in the following diagrams, which one of the diode is reverse biased ?
1

reverse biased

2

reverse biased

3

reverse biased

4

reverse biased

30
PYQ 2005
medium
physics ID: neet-ug-
Zener diode is used for
1

producing oscillations in an oscillator

2

amplification

3

stabilisation

4

rectification

31
PYQ 2005
medium
physics ID: neet-ug-
Application of a forward bias to a p-n junction:
1

increases the number of donors on the n-side

2

increases the electric field in the depletion zone

3

increases the potential difference across the depletion zone

4

widens the depletion zone

32
PYQ 2005
medium
physics ID: neet-ug-
Choose the only false statement from the following
1

Substances with energy gap of the order of 10 eV are insulators

2

The conductivity of a semiconductor increases with increases in temperature

3

In conductors the valence and conduction bands may overlap

4

The resistivity of a semiconductor increases with increase in temperature

33
PYQ 2005
medium
physics ID: neet-ug-
Carbon, silicon and germanium atoms have four valence electrons each. Their valence and conduction bands are separated by energy band gaps represented by (Eg)C , (Eg)Si and (Eg)Ge respectively. Which one of the following relationships is true in their case?
1

(Eg)C >(Eg)Si

2

(Eg)C = (Eg)Si

3

(Eg)C < (Eg)Ge

4

(Eg)C < (Eg)Si

34
PYQ 2005
medium
physics ID: neet-ug-
In a p-n junction photo cell, the value of the photo-electromotive force produced by monochromatic light is proportional to
1
The barrier voltage at the p-n junction.
2
The intensity of the light falling on the cell.
3
The frequency of the light falling on the cell.
4
The voltage applied at the p-n junction.
35
PYQ 2006
medium
physics ID: neet-ug-
A transistor is operated in common emitter configuration at constant collector voltage VC = 1.5 V such that a change in the base current from 100 µA to 150 µA produces a change in the collector current from 5 mA to 10 mA. The current gain (β) is :
1
50
2
70
3
100
4
125
36
PYQ 2006
medium
physics ID: neet-ug-
A forward biased diode is :
1
-4V to -3V
2
3V to 5V
3
-2V to +2V
4
0V to -2V
37
PYQ 2006
medium
physics ID: neet-ug-
A transistor-oscillator using a resonant circuit with an inductor L (of negligible resistance) and a capacitor C in series produce oscillations of frequency f. If L is doubled and C is changed to 4C, the frequency will be :
1
2
8f
3
4
2f
38
PYQ 2006
medium
physics ID: neet-ug-
The following figure shows a logic gate circuit with two inputs A and B and the output C. The voltage waveform of A, B and C are as shown below:
logic gate circuit with two inputs A and B and the output C

The logic circuit gate is:
1
AND gate
2
NAND gate
3
NOR gate
4
OR gate
39
PYQ 2008
easy
physics ID: neet-ug-
A photodiode is made of a material with a band gap of . The minimum frequency of the radiation that can be absorbed by the material is nearly (he = 1240 eV nm)
40
PYQ 2010
medium
physics ID: neet-ug-
Zener diode is used for
1

producing oscillations in an oscillator

2

amplification

3

stabilisation

4

rectification

41
PYQ 2010
easy
physics ID: neet-ug-
For transistor action (1) Base, emitter and collector regions should have similar size and doping concentrations. (2) The base region must be very thin and lightly doped. (3) The emitter-base junction is forward biased and base-collector junction is reverse biased. (4) Both the emitter-base junction as well as the base-collector junction are forward biased. Which one of the following pairs of statements is correct?
1
(4) and (1)
2
(1) and (2)
3
(2) and (3)
4
(3) and (4)
42
PYQ 2010
medium
physics ID: neet-ug-

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

1
NOR gate
2
OR gate
3
AND gate
4
NAND gate
43
PYQ 2010
easy
physics ID: neet-ug-
The device that can act as a complete electronic circuit is
1
junction diode
2
integrated circuit
3
junction transistor
4
zener diode
44
PYQ 2010
medium
physics ID: neet-ug-
A common emitter amplifier has a voltage gain of , an input impedance of and an output impedance of The power gain of the amplifier is
1
500
2
1000
3
1250
4
50
45
PYQ 2011
medium
physics ID: neet-ug-
A Zener diode, having breakdown voltage equal to , is used in a voltage regulator circuit shown in figure. The current through the diode is
1
5 mA
2
10 mA
3
15 mA
4
20 mA
46
PYQ 2012
medium
physics ID: neet-ug-
and both have same lattice structure; having bonding electrons in each. However, is insulator where as is intrinsic semiconductor. This is because
1
In case of C the valence band is not completely filled at absolute zero temperature
2
In case of C the conduction band is partly filled even at absolute zero temperature
3
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
4
The four bonding electron s in the case of C lie in the third orbit, whereas for Si they lie in the fourth orbit
47
PYQ 2013
medium
physics ID: neet-ug-
In which of the following statements, the obtained impure semiconductor is of -type ?
1
Germanium is doped with bismuth
2
Silicon is doped with antimony
3
Germanium is doped with gallium
4
Silicon is doped with phosphorus
48
PYQ 2013
easy
physics ID: neet-ug-
In an unbiased junction, holes diffuse from the -region to -region because of
1
The attraction of free electrons of -region.
2
The higher hole concentration in -region than that in -region.
3
The higher concentration of electrons in the -region than that in the -region.
4
The potential difference across the p-n junction.
49
PYQ 2013
medium
physics ID: neet-ug-
In a common emitter amplifier having a voltage gain , the transistor used has transconductance and current gain . If the above transistor is replaced with another one with transconductance and current gain , the voltage gain will be :
1
2
3
4
50
PYQ 2014
medium
physics ID: neet-ug-
The given graph represents characteristic for a semiconductor device.

Which of the following statement is correct?
1
It is characteristic for solar cell where, point represents open circuit voltage and point short circuit current.
2
It is for a solar cell and points and represent open circuit voltage and current, respectively.
3
It is for a photodiode and points and represent open circuit voltage and current, respectively.
4
It is for a LED and points and represent open circuit voltage and short circuit current, respectively.
51
PYQ 2016
medium
physics ID: neet-ug-
For transistor amplifier, the audio signal voltage across the collector resistance of is . If the current amplification factor of the transistor is and the base resistance is , then the input signal voltage is
1
10 mV
2
20 mV
3
30 mV
4
15 mV
52
PYQ 2016
medium
physics ID: neet-ug-
Consider the junction diode as ideal. The value of current flowing through is :
Consider the junction diode as ideal
1
2
3
4
53
PYQ 2016
medium
physics ID: neet-ug-
A transistor is connected to common emitter configuration in a given amplifier. A load resistance of is connected in the collector circuit and the voltage drop across it is . If the current amplification factor is and the input resistance of the circuit is , the voltage gain and the power gain of the amplifier will respectively be
1
3.69, 3.84
2
4 , 4
3
4, 3.69
4
4, 3.84
54
PYQ 2017
medium
physics ID: neet-ug-
The given electrical network is equivalent to :
1
OR gate
2
NOR gate
3
NOT gate
4
AND gate
55
PYQ 2017
medium
physics ID: neet-ug-
In a common emitter transistor amplifier the audio signal voltage across the collector is . The resistance of collector is . If current gain is and the base resistance is , the voltage and power gain of the amplifier is :
1
15 and 200
2
150 and 15000
3
20 and 2000
4
200 and 1000
56
PYQ 2017
medium
physics ID: neet-ug-
In a common emitter transistor amplifier the audio signal voltage across the collector is 3 V. The resistance of collector is 3 kΩ. If current gain is 100 and the base resistance is 2 kΩ, the voltage and power gain of the amplifier is
1
200 and 1000
2
15 and 200
3
150 and 15000
4
20 and 2000
57
PYQ 2018
medium
physics ID: neet-ug-
In the circuit shown in the figure, the input voltage is and .The values of and are given by
1
2
3
4
58
PYQ 2018
medium
physics ID: neet-ug-
In a junction diode, change in temperature due to heating
1
affects only reverse resistance
2
affects only forward resistance
3
does not affect resistance of p-n junction
4
affects the overall V -I characteristics of p-n junction
59
PYQ 2018
medium
physics ID: neet-ug-
In the combination of the following gates the output can be written in terms of inputs and as
1
2
3
4
60
PYQ 2018
medium
physics ID: neet-ug-
In the circuit shown in the figure, the input voltage is and .The values of and are given by
1
2
3
4
61
PYQ 2018
medium
physics ID: neet-ug-
In a junction diode, change in temperature due to heating
1
affects only reverse resistance
2
affects only forward resistance
3
does not affect resistance of p-n junction
4
affects the overall V -I characteristics of p-n junction
62
PYQ 2019
medium
physics ID: neet-ug-
For a p-type semiconductor, which of the following statements is true ?
1
Holes are the majority carriers and pentavalent atoms are the dopants.
2
Electrons are the majority carriers and pentavalent atoms are the dopants.
3
Electrons are the majority carriers and trivalent atom >re the dopants.
4
Holes are the majority carriers and trivalent atoms are the dopants.
63
PYQ 2020
medium
physics ID: neet-ug-
The solids which have negative temperature coefficient of resistance are :
1
metals
2
insulators only
3
semiconductors only
4
insulators and semiconductors
64
PYQ 2021
medium
physics ID: neet-ug-
For the given circuit, the input digital signals are applied at the terminals A, B and C. What would be the output at the terminal y?
input digital signals are applied at the terminals
1

2

3

4

65
PYQ 2021
medium
physics ID: neet-ug-
The electron concentration in an n-type semiconductor is the same as the hole concentration in a p-type semiconductor. An external field (electric) is applied across each of them. Compare the currents in them
1

No current will flow in p-type, current will only flow in n-type

2

current in n-type=current in p-type

3

current in p-type > current in n-type

4

current in n-type > current in p-type

66
PYQ 2021
medium
physics ID: neet-ug-
Consider the following statements (A) and (B) and identify the correct answer.
(A) A zener diode is connected in reverse bias when used as a voltage regulator.
(B) The potential barrier of the p-n junction lies between 0.1 V to 0.3 V.
1

(A) is incorrect but (B) is correct

2

(A) and (B) both are correct

3

(A) and (B) both are incorrect

4

(A) is correct and (B) is incorrect

67
PYQ 2022
medium
physics ID: neet-ug-
In half wave rectification, if the input frequency is 60 Hz, then the output frequency would be:
1
Zero
2
30 Hz
3
60 Hz
4
120 Hz
68
PYQ 2022
medium
physics ID: neet-ug-
The truth table for the given logic circuit is:
1
A B C
0 0 0
0 1 1
1 0 1
1 1 0
2
A B C
0 0 1
0 1 0
1 0 0
1 1 1
3
A B C
0 0 1
0 1 0
1 0 1
1 1 0
4
A B C
0 0 0
0 1 1
1 0 0
1 1 1
69
PYQ 2022
medium
physics ID: neet-ug-
In the given circuits (a), (b) and (c), the potential drop across the two p-n junctions are equal in:
1
Circuit (a) only
2
Circuit (b) only
3
Circuit (c) only
4
Both circuits (a) and (c)
70
PYQ 2023
hard
physics ID: neet-ug-
A full wave rectifier circuit consists of two p-n junction diodes, a centre-tapped transformer, capacitor and a load resistance. Which of these components remove the ac ripple from the rectified output?
1
Load resistance
2
A centre-tapped tranformer
3
p-n juntion diodes
4
Capacitor
71
PYQ 2023
medium
physics ID: neet-ug-
Given below are two statements:
Statement I: Photovoltaic devices can convert optical radiation into electricity.
Statement II: Zener diode is designed to operate under reverse bias in breakdown region.
In the light of the above statements, choose the most appropriate answer from the options given below:
1

Statement I is incorrect but Statement II is correct.

2

Statement I and Statement II are incorrect.

3

Both Statement I and Statement II are correct.

4

Statement I is correct but Statement II is incorrect

72
PYQ 2023
medium
physics ID: neet-ug-

For the following logic circuit, the truth table is:

logic circuit

1

2

3

4

73
PYQ 2024
medium
physics ID: neet-ug-
Problem fig
The I-V characteristics shown above are exhibited by a:
1
Light emitting diode
2
Zener diode
3
Photodiode
4
Solar cell

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