Sri Chaitanya IIT Academy., India.
A.P, TELANGANA, KARNATAKA, TAMILNADU, MAHARASHTRA, DELHI, RANCHI
A right Choice for the Real Aspirant
ICON Central Office – Madhapur – Hyderabad
SEMI CONDUCTOR DEVICES
SEMI CONDUCTOR DEVICES
1(O). Which of the following circuits represents a forward biased diode?
(22-01-25 shift-1 Q.No: 39)
A)
B)
C) D)
E)
Choose the correct answer from the options given below.
1) (C) and (E) only 2) (A) and (D) only
3) (B), (D) and (E) only 4) (B) ,(C) and (E) only
Key: 4
Sol: Conceptual
1(A). Which of the following represents a reverse bias
0v
2v
1
2
1 0 v
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15 v 10 v
3 4
1 0 v 5v
2v
5
4v
Choose correct answer from options given below.
1) (C ) and ( E) only 2) (A) only
3) (B) , (D) and (E) only 4) (B) , (C) and (E) only
Key : 2
Sol: In reverse bias , P- side is connected to lower potential and n-side is connected to
gieher potential .
1(B). The diode in given circuit is
d i
L2 0
d t
1) forward biased 2) reverse biased
3) bias can be predicted based on current 4) none of the above
Key : 2
Sol: Reverse biased , use KVL and find potential across the diode
1(C). Statement –I : In forward bias, P side of diode is necessarily connected to positive
terminal of battery and n side is necessarily connected to negative terminal of battery
Statement –II: If P side of diode is connected to higher potential and n side of diode is
connected to lower potential , then diode is forward biased
1) statement –I , statement –II are true
2) statement –I , statement –II are false
3) statement –I is false statement –II is true
4) statement –I is true statement –II is false
Key : 1
Sol: Conceptual
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TOPIC: semi condutors
2(O) The truth table for the circuit given below is : (29-01-25 shift-2 Q.No:43)
Ans : 1
2a) The truth table given in fig represents
1) OR – gate 2) NAND – Gate 3) AND – Gate 4) NOR – Gate
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Key : 1
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Sol :
2b) In a communication system only one percent frequency of signal of wavelength
800nm can be used
as band width. How many channel of 6MHz band width can be broadcast with this ?
(Take c 3 108 m / s)
1) 3.75 10 2) 3.85 10 4) 4.87 10
6 6 5
3) 6.25 105
Key : 3
total bandwidth available
Sol : Number of channels for signals bandwidth of TV signal
6.255 105
3(O). [28 -01-25 shift-2]
In the circuit shown here, assuming threshold voltage of diode is neligibly small, then
voltage VAB is correctly represented by:
1)
2)
3)
3(a). Different voltages are applied across a P-N junction and the currents are measured for
each value. Which of the following graphs is obtained between voltage and current ?
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(c)
Key: c
Sol: PN junction has low resistance in one direction of potential difference +V, so a large
current flows (forward biasing). It has a high resistance in the opposite potential
difference direction –V, so a very small current flows ( reverse biasing)
3(b). Calculate the voltage drop across 5 resistance and current passing through the zener
diode for the circuit given below:
1)13.995amp 2)14.225amp 3)254.2amp 4)12.25amp
Key: 1
Sol: Sine the voltage across the zener diode, V2 50volt
Voltage drop across 5 resistor = 120 50 70volt
70
I 14amp
Current through 5 5
Current through load resistor of 10k
Vz 50
IL 5 103 amp
RL 10k
Therefore, current through the Zener diode
I z I I L 14 5 103 amp. 13995amp
4(O).
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For the circuit shown above, equivalent GATE is: (29-01-25 shift-1 Q.No:43)
1) AND gate 2) OR gate 3) NAND gate 4) NOT gate
Key: 2
Sol:
Q A.B . A B A.B A B A.B A B A B 1 B A BOR gate
4(a)
For the circuit shown above, equivalent gate is
1) NAND 2) NOR 3) XOR 4) XNOR
Key: 3
Sol:
Y A B A.B
This output represents an XOR gate
4(b) For the circuit shown below equivalent gate is
1) AND 2) NOR 3) OR 4) NAND
Key: 4
Sol:
y AB
NAND gate
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TOPIC : Semi conductor devices
5(O).
A B Y
0 0 1
0 1 0
1 0 0
1 1 1
To obtain the given table, following logic gate should be placed at G:
[22-01-25 shift-2 Q.No:39]
1)NAND Gate 2) NOR Gate 3) OR Gate 4) AND Gate
Ans : No Option
Sol :
A B B A.B B. A AND OR NAND NOR
0 0 1 0 0 0 0 1 1
0 1 0 0 0 0 0 1 1
1 0 1 1 1 1 1 0 0
1 1 0 0 0 0 0 1 1
The output is not match with following option
5(a) The output of the given circuit is
1) 0 2) B 3) A.B 4) A+B
Ans: 1
Sol: Conceptual
5(b) Identify the operations performed by the circuit given below
1) NAND 2) OR 3) AND 4) NOT
Ans: 3
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Solution: A B C A.B.C
6(O). Refer to the circuit diagram given in the figure. Which of the following observations
are correct?
1) Total resistance of circuit is 6
2) Current in Ammeter is 1A
3) Potential across AB is 4 Volts.
4) Potential across CD is 4 Volts
5) Total resistance of the circuit is 8
Choose the correct answer from the options given below: [23-01-25 shift-1 Q.No:29]
1) A,C and D Only 2) A,B and C Only
3) A,B and D Only 4) B,C and E Only
6(A). Refer to the circuit diagram given in the figure. Which of the following observation in
the figure. Which of the following observations are correct.
A) Total resistance of circuit is 3
B) Current in Ammeter is 1A
C) Potential difference across AB is 1V
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D) Total resistance of the circuit is 6
1) A,B only 2) B,C,D only 3) A,B,C,D only 4) B,C,D,E only
Key : (3)
Sol:
Diode in forward bias hence total resistance of circuit in (2 + 1) = 3
Current through ammeter is 1A
VAB 0.5 2 1V
VCD 1 2 2V
6B. Refer to the circuit diagram given in figure which of the following observation are
correct.
A) Total resistance of circuit is 9
5
B) Current in Ammeter is A
9
5
C) Potential across AB is V
3
5
D) Potential across CD is V
3
E) Total resistance of the circuit 9
1) A,C only 2) B,C,D only 3) A,C,D only 4) A,B,C,E only
Key : (4)
Sol : Diode in forward bias
Total vertex in circuit 6+3= 9
5
Current in ammeter
9
5 5
Voltage area VAB 6 V
18 3
5 10
VCD 6 V
9 3
6C. Refer to the circuit diagram given in figure which of the following observation an
curved.
A) Total resistance of circuit is 4
B) Current in Ammeter is 1A
C) Potential across AB is 1V
D) Potential across CD is 3 Volt
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E) Total resistance of the circuit is 3
1) C,D only 2) A,B,C,D only 3) A,B,C only 4) A,C only
Key : (4)
Sol: Diode Forward bias
Total vetex 3 1 4
4
Current in ammeter 1A
4
1
VAD 2 1V
2
VCD 3 1 3V
6(D). Refer to the circuit diagram given in figure which of the following observations are
correct.
A) Total resistance of circuit is 7.5
B) Current in ammeter is 1A
C) Potential across CD is 5V
D) Potential across AB is Zero
E) Total resistance in current is 10
1) B,C only 2) A,C,D only 3) B,D,E only 4) A,B,C,D only
Key: (4)
Sol:
Diode reverse bias
5 5
Total reaction 5 5 2.5 7.5
55
10
Current in ammeter is 1A
w
Partial VCD 5 1 5V
Since diode is reverse bias condition no current flow through it
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6(E). Refer to the circuit diagram given in fig which of the following observation are correct.
A) Total resistance of the circuit is 6
8
B) Current in ammeter is A
3
8
C) Potential across AB is V
3
16
D) Potential across CD is V
3
1) A,B,C only 2) B,C,D only 3) B,D only 4) A,B,D only
Key : (2)
Sol:
Forward bias
Total resistor 2 1 3
8
Current in Ammeter A
3
8
Partial area VAB
3
16
Partial area VCD ohm
3
TOPIC : SEMI CONDUCTOR DEVICES
7(O). What is the current through the battery in the circuit shown below?
[23-01-25 SHIFT-2 Q.NO: 7 ]
1) 1.0A 2) 0.5A 3) 1.5A 4) 0.25A
Key: 2
RR 20 20
Sol: R eq 1 2 =10
R1 R2 20 20
V iR
V 5
i 0.5 A
R 10
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7(a). What is the current through the battery in circuit shown below.
a). 0.4 A b)0.2A c)1A d)0.3A
Key: c
R1R2 10 10 100
Sol: Req 5
R1 R2 10 10 20
V 5
V iR i i 1A
R 5
7(b). What is the current through the battery in circuit shown below?
a) 2A b) 0.4A c) 0.25A d) 0.5A
Key: c
Sol: Req 20
V 5 1
i 0.25 A
R 20 4
8(O). Consider the following statements:
A. The junction area of solar cell is made very narrow compared to a photo diode.
B. Solar cells are not connected with any external bias.
C. LED is made of lightly doped p-n junction.
D. Increase of forward current results in continuous increase of LED light intensity.
E. LEDs have to be connected in forward bias for emission of light.[24-01-25 SHIFT-2
Q.NO:39]
1) B, D, E Only 2) A, C Only 3) A, C, E Only 4) B, E Only
Key: 4
Sol: Conceptual
8(a). Which of the following statements regarding Light Emitting Diodes (LEDs) is
incorrect?
1. LEDs require forward bias for light emission
2. LEDs are made of heavily doped p-n junctions
3. The intensity of light increases with forward current
4. LEDs operate efficiently in reverse bias
Key:4
Solution
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Statement 1: LEDs require forward bias for light emission(Correct)
Statement 2: LEDs are made of heavily doped p-n junctions (Correct)
Statement 3: Light intensity increases with forward current (Correct)
Statement 4: LEDs operate efficiently in reverse bias (Incorrect, LEDs do not work
efficiently in reverse bias)
8.(b). Consider the following statements about Zener diodes
A. Zener diodes operate in reverse bias in the breakdown region
B. Zener diodes are used as voltage regulators
C. The breakdown voltage of a Zener diode decreases with temperature
D. Zener diodes allow large current flow in forward bias
Which of the following options is correct?
1. A and B only 2. A, B, and C only
3. B and D only 4. A. C. and D only
Key:2
Solution
A Zener diodes are designed to operate in reverse bias in the breakdown region.
(Correct)
B They are widely used as voltage regulators to maintain a constant voltage. (Correct)
C The breakdown voltage decreases with temperature due to changes in carrier
movement. (Correct)
D Zener diodes allow small current in forward bias, not large current.
Final Answer: Option 2 (A, B, and C only)
8.(c). A photodiode is operated in reverse bias because:
1. It increases the depletion width and reduces junction capacitance
2. It allows higher dark current
3. It reduces carrier recombination at the junction
4. Both 1 and 3
Key:4
Solution
Reverse bias increases the depletion width, reducing junction capacitance and
improving sensitivity. (Correct)
It also reduces carrier recombination, allowing efficient conversion of light into
current. (Correct)
Dark current is an unwanted effect, but it's not the main reason for reverse bias
operation.
Final Answer: Option 4 (Both 1 and 3)
TOPIC: SEMI CONDUCTOR DEVICES
9(O).The output of the circuit is low (zero) for : [24-01-25 SHIFT-2 Q.NO:42]
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A) X=0,Y=0 B) X=0,Y=1 C) X=1,Y=0 D) X=1,Y=1
Choose the Correct answer from the options given below.
1) (A),(C) and (D) only 2) (A),(B) and (C) Only
3) (A),(B) and (D) only 4) (B),(C) and (D) only
Key: 4
Sol:
Output x y
=0
If x 1, y 1 Or x 0, y 1 Or x=1 , y=1
9(a). The output of the logic circuit given below represents which gate?
1)OR 2)NOR 3)AND 4)NAND
Key: 4
Sol: The Boolean expression for the circuit is
Q A B B B Q A B Q A.B Q A.B A.B
9(b). In the following digital circuit , what will be the output at ‘Z’, when the input (A,B)
are (1,0) and (0,0)?
1) 1,1 2)0,0 3)1,0 4)0,1
Key: 2
Sol: The Boolean expression is
Z A.B.( A B) ( A. B)
Z A.B (property (A.B)+A=A)
Z A. B
Substituting (A,B) (1,0) , z=0
And (0,0), z=0
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10(O).
a) b)
c) d)
Key: a
10(A). The output of the circuit is low (zero)
(A) X = 0, Y= 0 (B) X = 0, Y= 1 (C) X = 1, Y= 0 (D) X = 1, Y=0
Choose the correct answer from the options given below :
(1) (A), (C) and (D) only
(2) (A), (B) and (C) only
(3) (B), (C) and (D) only
(4)(A),(B)and(D) only
Key: 3
Sol:
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