Topic 8 : Logic Gate

1 . The given circuit is equivalent to: ⇒  ( NEET 2023 Manipur)

NEET 2023 Manipur Physics - Semiconductor Electronics Question 1 English

A.

NEET 2023 Manipur Physics - Semiconductor Electronics Question 1 English Option 1

B.

NEET 2023 Manipur Physics - Semiconductor Electronics Question 1 English Option 2

C.

NEET 2023 Manipur Physics - Semiconductor Electronics Question 1 English Option 3

D.

NEET 2023 Manipur Physics - Semiconductor Electronics Question 1 English Option 4

The Correct Answer is Option (D)

Y = A + B = A . B = A . B

AND gate

for AND gate

NEET 2023 Manipur Physics - Semiconductor Electronics Question 1 English Explanation

2. For the following logic circuit, the truth table is: ⇒  ( NEET 2023)

NEET 2023 Physics - Semiconductor Electronics Question 7 English

A.

A B Y
0 0 0
0 1 1
1 0 1
1 1 1

B.

A B Y
0 0 1
0 1 0
1 0 1
1 1 0

C.

A B Y
0 0 0
0 1 0
1 0 0
1 1 1

D.

A B Y
0 0 1
0 1 1
1 0 1
1 1 0

The Correct Answer is (A)

y = A B = A + B

  = ( A + B )   OR Gate

A B Y
0 0 0
0 1 1
1 0 1
1 1 1

3. Identify the equivalent logic gate represented by the given circuit ⇒  (NEET 2022 Phase 2)

NEET 2022 Phase 2 Physics - Semiconductor Electronics Question 10 English

A. NAND

B. OR

C. NOR

D. AND

The Correct Answer is (B)

The given circuit clearly indicates that the bulb will glow when either of the switches are closed.

The corresponding truth table will be

Input A Input B Output Y
0 0 0
0 1 1
1 0 1
1 1 1

This suggests that it will correspond to OR gate.

4. The truth table for the given logic circuit is⇒  (NEET 2022 Phase 1)

NEET 2022 Phase 1 Physics - Semiconductor Electronics Question 13 English

A.

NEET 2022 Phase 1 Physics - Semiconductor Electronics Question 13 English Option 1

B.

NEET 2022 Phase 1 Physics - Semiconductor Electronics Question 13 English Option 2

C.

NEET 2022 Phase 1 Physics - Semiconductor Electronics Question 13 English Option 3

D.

NEET 2022 Phase 1 Physics - Semiconductor Electronics Question 13 English Option 4

The Correct Answer is (C)

C = A . B + A . B

C = ( A + A ) B

C = B

The truth table would be

NEET 2022 Phase 1 Physics - Semiconductor Electronics Question 13 English Explanation

NEET 2022 Phase 1 Physics - Semiconductor Electronics Question 13 English Explanation

6. 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? ⇒  (NEET 2021)


NEET 2021 Physics - Semiconductor Electronics Question 16 English 2

A.

NEET 2021 Physics - Semiconductor Electronics Question 16 English Option 1

B.

NEET 2021 Physics - Semiconductor Electronics Question 16 English Option 2

C.

NEET 2021 Physics - Semiconductor Electronics Question 16 English Option 3

D.

NEET 2021 Physics - Semiconductor Electronics Question 16 English Option 4

The Correct Answer is (C)

Y = A B + B C

NEET 2021 Physics - Semiconductor Electronics Question 16 English Explanation

7. The correct Boolean operation represented by the circuit diagram drawn is :⇒  (NEET 2019)

NEET 2019 Physics - Semiconductor Electronics Question 25 English

A. OR

B. NAND

C. NOR

D. AND

The Correct Answer is (B)

From the given logic circuit LED will glow, when voltage across LED in high. This can be verified by the given truth table.

NEET 2019 Physics - Semiconductor Electronics Question 25 English Explanation

Boolean expression Y = A . B

This is output of NAND gate.

8. In the combination of the following gates the output Y can be written in terms of inputs A and B as ⇒  (NEET 2018)

NEET 2018 Physics - Semiconductor Electronics Question 23 English

A. A . B

B. A . B + A . B

C. A . B + A . B

D. A + B

The Correct Answer is ()

NEET 2018 Physics - Semiconductor Electronics Question 23 English Explanation

9. The given electrical network is equivalent to ⇒  (NEET 2017)

NEET 2017 Physics - Semiconductor Electronics Question 105 English

A. OR gate

B. NOR gate

C. NOT gate

D. AND gate

The Correct Answer is (B)

NEET 2017 Physics - Semiconductor Electronics Question 105 English Explanation

y1 = A + B

y2 = y 1 + y 1

= A + B

y = y 2 = A + B

So it is NOR gate.

10. For CE transistor amplifier, the aufio signal voltage across the collector resistance of 2 k Ω is 4 V. If the current amplification factor of the transistor is 100 and the base resistance is 1 k Ω , then the input signal voltage is ⇒  (NEET 2016 Phase 2)

A. 10 mV

B. 20 mV

C. 30 mV

D. 15 mV

The Correct Answer is (B)

Voltage gain, A = β R C R B = 100 × 2000 1000 = 200

Also, A = V 0 V i

V i = V 0 A = 4 200 = 20 mA

11. What is the output Y in the following circuit, when all the three inputs A, B, C are first 0 and then 1 ? ⇒  (NEET 2016 Phase 2)

NEET 2016 Phase 2 Physics - Semiconductor Electronics Question 100 English

A. 0, 1

B. 0, 0

C. 1, 0

D. 1, 1

The Correct Answer is (C)

Applying De Morgan’s law:

Output Y = [(A ⋅ B) ⋅ C]' = A' + B' + C'

When A, B, C are 0 Y = 1

When A, B, C are 1 Y = 0

12. To get output 1 for the following circuit, the correct choice for the input is ⇒  ( NEET 2016 Phase 1)

NEET 2016 Phase 1 Physics - Semiconductor Electronics Question 99 English

A. A = 1, B = 1, C = 0

B. A = 1, B = 0, C = 1

C. A = 0, B = 1, C = 0

D. A = 1, B = 0, C = 0

The Correct Answer is (B)

Output of the circuit, Y = (A + B)·C

Y = 1 if C = 1 and A = 0, B = 1

or A = 1, B = 0 or A = B = 1

13. Which logic gate is represented by the following combination of logic gates ? ⇒  ( AIPMT 2015 Cancelled Paper)

AIPMT 2015 Cancelled Paper Physics - Semiconductor Electronics Question 94 English

A. AND

B. NOR

C. OR

D. NAND

The Correct Answer is (A)

The Boolean expression of this arrangement is

Y = A + B = A + B = A.B

Thus, the combination represents AND gate.

14. The output from a NAND gate is divided into two in parallel and fed to another NAND gate. The resulting gate ⇒  (NEET 2013 (Karnataka))

is a NEET 2013 (Karnataka) Physics - Semiconductor Electronics Question 87 English

A. AND gate

B. NOR gate

C. OR gate

D. NOT gate

The Correct Answer is (A)

C' = A . B

C = A . B = A.B

Hence the resultant gate is AND gate.

15. The output (X) of the logic circuit shown ion figure will be ⇒  (NEET 2013)

NEET 2013 Physics - Semiconductor Electronics Question 88 English

A. X = A . B

B. A + B

C. X = A . B

D. X = A . B

The Correct Answer is (C)

The output of the given logic circuit is

X = A . B = A.B

16. To get an output Y= 1 in given circuit which of the following input will be correct ?⇒  (AIPMT 2012 Mains)

AIPMT 2012 Mains Physics - Semiconductor Electronics Question 78 English

A. A 1,  B 0,  C 0

B. A 1,  B 0,  C 1

C. A 1,  B 1,  C 0

D. A 0,  B 1,  C 0

The Correct Answer is (B)

AIPMT 2012 Mains Physics - Semiconductor Electronics Question 78 English Explanation

The Boolen expression for the given combination is

output Y = (A + B) · C

So it is clear that Y = 1, when A = 1, B = 0 and C = 1

17. 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 ⇒  (AIPMT 2012 Prelims)

AIPMT 2012 Prelims Physics - Semiconductor Electronics Question 80 English

A. OR gate

B. NOR gate

C. AND gate

D. NAND gate

The Correct Answer is (A)

The truth table is AIPMT 2012 Prelims Physics - Semiconductor Electronics Question 80 English Explanation
The logic circuit is OR gate.

18. Symbolic representation of four logic gates are shown as ⇒  ( AIPMT 2011 Prelims)

AIPMT 2011 Prelims Physics - Semiconductor Electronics Question 74 English

AIPMT 2011 Prelims Physics - Semiconductor Electronics Question 74 English

AIPMT 2011 Prelims Physics - Semiconductor Electronics Question 74 English

AIPMT 2011 Prelims Physics - Semiconductor Electronics Question 74 English

Pick out which ones are for AND, NAND and NOT gates, respectively

A. (ii), (iii) and (iv)

B. (iii), (ii) and (i)

C. (iii), (ii) and (iv)

D. (ii), (iv) and (iii)

The Correct Answer is (C)

AND, NAND and NOT gates are (ii), (iv) and (iii) respectively.

19. 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.

AIPMT 2010 Mains Physics - Semiconductor Electronics Question 65 English

The logic gate is ⇒  (AIPMT 2010 Mains)

A. NOR gate

B. OR gate

C. AND gate

D. NAND gate

The Correct Answer is (D)

It is clear from given logic circuit, that out put Y is low when both the inputs are high, otherwise it is high. Thus logic circuit is NAND gate.

20. To get an output Y = 1 in given circuit which of the following input will be correct ?

AIPMT 2010 Prelims Physics - Semiconductor Electronics Question 77 English ⇒  (AIPMT 2010 Prelims)

A. A 1,  B 0,  C 0

B. A 1,  B 0,  C 1

C. A 1,  B 1,  C 0

D. A 0,  B 1,  C 0

The Correct Answer is (B)

AIPMT 2010 Prelims Physics - Semiconductor Electronics Question 77 English Explanation

The Boolen expression for the given combination is

output Y = (A + B) · C

So it is clear that Y = 1, when A = 1, B = 0 and C = 1

21. The device that can act as a complete electronic circuit is ⇒  (AIPMT 2010 Prelims)

A. junction diode

B. integrated circuit

C. junction transistor

D. zener diode

The Correct Answer is (B)

Integrated circuit can act as a complete electronic circuit.

22. The symbolic representation of four logic gates are given below

AIPMT 2009 Physics - Semiconductor Electronics Question 62 English

The logic symbols for OR, NOT and NAND gates are respectively ⇒  (AIPMT 2009)

A. (iv), (i), (iii)

B. (iv), (ii), (i)

C. (i), (iii), (iv)

D. (iii), (iv), (ii)

The Correct Answer is (B)

OR gate, NOT gate and NAND gates are (iv), (ii) and (i) respectively.

23. A transistor is operated in common-emitter configuration at VC = 2V 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 ⇒  (AIPMT 2009)

A. 100

B. 150

C. 50

D. 75

The Correct Answer is (C)

Current gain, β = Δ I C Δ I B

= ( 10 5 ) × 10 3 ( 200 100 ) × 10 6 = 50

24. In the following circuit, the output Y for all possible inputs A and B is expressed by the truth table. ⇒  (AIPMT 2007)

AIPMT 2007 Physics - Semiconductor Electronics Question 56 English

A. A B Y 0 0 1 0 1 1 1 0 1 1 1 0

B. A B Y 0 0 1 0 1 0 1 0 0 1 1 0

C. A B Y 0 0 0 0 1 1 1 0 1 1 1 1

D. A B Y 0 0 0 0 1 0 1 0 0 1 1 1

The Correct Answer is (C)

Y' = A + B

Y = Y

Y = A + B

Y = A + B which is OR-gate.

25. The following figure shows a logic gate circuit with two inputs A and B and the output C. ⇒  (AIPMT 2006)

AIPMT 2006 Physics - Semiconductor Electronics Question 53 English 1

The voltage waveforms of A, B and C are as shown below.

AIPMT 2006 Physics - Semiconductor Electronics Question 53 English 2

The logic circuit gate is

A. OR gate

B. AND gate

C. NAND gate

D. NOR gate

The Correct Answer is (B)

The truth table corresponding to waveform is given by

A B C 1 1 1 0 1 0 1 0 0 0 0 0

The given logic circuit gate is AND gate.

26. The output of OR gate is 1 ⇒  ( AIPMT 2004)

A. if both inputs are zero

B. if either or both inputs are 1

C. only if both inputs are 1

D. if either inputs is zero

The Correct Answer is Option (B)

The truth table of OR gate is

A B Y 0 0 0 0 1 1 1 0 1 1 1 1

It is seen that output of OR gate is Y = A + B.
If both or any one has 1 input then output will be 1.

27. The given truth table is for which logic gate ⇒  (AIPMT 2002)

               A B Y 1 1 0 0 1 1 1 0 1 0 0 1

A. NAND

B. XOR

C. NOR

D. OR.

The Correct Answer is Option (A)

This truth table represents NAND gate.

28. The given truth table is for which logic gate ⇒  (AIPMT 2001)

               A B Y 1 1 0 0 1 1 1 0 1 0 0 1

A. NAND

B. XOR

C. NOR

D. OR

The Correct Answer is Option (A)

This truth table represents NAND gate. AIPMT 2001 Physics - Semiconductor Electronics Question 33 English Explanation