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Digital Circuits Mcqs

Q:

A full adder logic circuit will have __________

A) Two inputs and one output B) Three inputs and three outputs
C) Two inputs and two outputs D) Three inputs and two outputs
 
Answer & Explanation Answer: D) Three inputs and two outputs

Explanation: A full adder circuit will add two bits and it will also accounts the carry input generated in the previous stage. Thus three inputs and two outputs (Sum and Carry) are there. In case of half adder circuit, there are only two inputs bits and two outputs (SUM and CARRY).

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2236
Q:

On subtracting +28 from +29 using 2’s complement, we get ____________

A) 11111010 B) 111111001
C) 100001 D) 1
 
Answer & Explanation Answer: D) 1

Explanation: Not available for this question

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2006
Q:

In 1-to-4 multiplexer, if C1 = 1 & C2 = 1, then the output will be ___________

A) Y0 B) Y1
C) Y2 D) Y3
 
Answer & Explanation Answer: D) Y3

Explanation: Not available for this question

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1881
Q:

The octal number (651.124)8 is equivalent to ______

A) (1A9.2A)16 B) (1B0.10)16
C) (1A8.A3)16 D) (1B0.B0)16
 
Answer & Explanation Answer: A) (1A9.2A)16

Explanation: First, the octal number is converted to it’s equivalent binary form, by writing the binary equivalent of each digit in form of 3 bits. Then, the binary equivalent bits are grouped in terms of 4 bits and then for each of the 4-bits, the respective digit is written. Thus, the hexadecimal equivalent is obtained.
(651.124)8 = (110 101 001.001 010 100)2
= (110101001.001010100)2
= (0001 1010 1001.0010 1010)2
= (1A9.2A)16.

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1446
Q:

In a parallel in/parallel out shift register, D0 = 1, D1 = 1, D2 = 1, and D3 = 0. After three clock pulses, the data outputs are ________

A) 1110 B) 0001
C) 1100 D) 1000
 
Answer & Explanation Answer: B) 0001

Explanation: Parallel in parallel out gives the same output as input. Thus, after three clock pulses, the data outputs are 0001.

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1288
Q:

Complement of the expression A’B + CD’ is _________

A) (A’ + B)(C’ + D) B) (A + B’)(C’ + D)
C) (A’ + B)(C’ + D) D) (A + B’)(C + D’)
 
Answer & Explanation Answer: B) (A + B’)(C’ + D)

Explanation: (A’B + CD’)’ = (A’B)'(CD’)’ (By DeMorgan’s Theorem) = (A” + B’)(C’ + D”) (By DeMorgan’s Theorem) = (A + B’)(C’ + D).

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1189
Q:

Simplify Y = AB’ + (A’ + B)C.

A) AB’ + C B) AB + AC
C) A’B + AC’ D) AB + A
 
Answer & Explanation Answer: A) AB’ + C

Explanation: Y = AB’ + (A’ + B)C = AB’ + (AB’)’C = (AB’ + C)( AB’ + AB’) = (AB’ + C).1 = (AB’ + C).

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1160
Q:

On subtracting (01010)2 from (11110)2 using 1’s complement, we get ____________

A) 01001 B) 11010
C) 10101 D) 10100
 
Answer & Explanation Answer: D) 10100

Explanation: Not available for this question

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1110