MCQ on Combinational Logic Circuits
MCQ on Combinational Logic Circuits, Multiple choice questions on combinational logic circuits, MCQ on Half Adder, MCQ on Full Adder, Objective Questions on Combinational logic, MCQ on Look Ahead Carry Adder, Engineering MCQ, Multiple Choice Question based on Engineering, Digital Electronics MCQ
Multiple Choice Questions
- A half adder has
- 2 inputs and 2 outputs
- 2 inputs and 3 outputs
- 3 inputs and 2 outputs
- 3 inputs and 3 outputs
Answer: 2 inputs and 2 outputs
2. A full adder has
- 2 inputs and 3 outputs
- 2 inputs and 2 outputs
- 3 inputs and 2 outputs
- 3 inputs and 3 outputs
Answer: 2 inputs and 2 outputs
3. Half adders are used for addition of
- Three bits
- Four bits
- Five bits
- Two bits
Answer: Two bits
4. Full adders are used for addition of
- Three bits
- Four bits
- Five bits
- Two bits
Answer: Three bits
5. Ripple carry adders use ________ to add two n-bit numbers.
- Two half adders
- Two full adders
- One half adder and one full adder
- None of the above
Answer: One half adder and one full adder
6. An n-bit ripple carry adder having ‘n’ adders has time delay T equal to
- T
- nT
- 1
- 1–T
Answer: nT
7. A 1-to-8 demultiplexer has ________ select input lines.
- 2 select input lines
- 3 select input lines
- 8 select input lines
- 4 select input lines
Answer: 4 select input lines
8. The circuit containing 2n input lines and n output lines, that performs converse of decoding is called as
- Subtractor
- Decoder
- Multiplexer
- Encoder
Answer: Encoder
9. In the full adder, if the sum is S and carry is C then
- S = 1 when two or more inputs are unity
- C = 1 when two or more inputs are unity
- S = 1 when all inputs are unity
- C = 1 when all inputs are unity
Answer: C = 1 when two or more inputs are unity
10. The data from input to a selected output line is directed by
- Multiplexer
- Coder
- Adders
- Demultiplexer
Answer: Demultiplexer
11. A 32 to 1 multiplexer has the following terminals
- 32 outputs, one input and 5 control signals
- 32 inputs, one output and 5 control signals
- 5 inputs, one control signal and 32 outputs
- 5 inputs 32 control signals and one output
Answer: 32 inputs, one output and 5 control signals
12. If a multiplexer can switch one of 16 data inputs to its output then how many inputs does it have?
- 16 data inputs and 1 select inputs
- 8 data inputs and 2 select inputs
- 16 data inputs and 4 select inputs
- 2 data inputs and 8 select inputs
Answer: 16 data inputs and 4 select inputs
13. A half adder circuit is constructed using
- EX-OR gate and NOR gate
- EX-OR gate and OR gate
- EX-OR gate and AND gate
- EX-OR gate and NAND gate
Answer: EX-OR gate and AND gate
14. Demultiplexer is a device used to change
- Sum two parallel data
- Serial data to parallel data
- Parallel data to serial data
- Sum two serial data
Answer: Serial data to parallel data
15. A device that coverts binary words into alphanumeric characters is
- Decoder
- Encoder
- Multiplexer
- Demultiplexer
Answer: Decoder
16. To achieve proper functioning of the encoder, which of the following condition is to be satisfied?
- All inputs are active
- Only one of the inputs is active
- No input is active
- All inputs are at logic 0
Answer: Only one of the inputs is active
17. The addition of two binary variables A and B results into a SUM and CARRY equal to
- Sum = A’B’ + AB, Carry = AB
- Sum = AB + B, carry = A’B
- Sum = AB’ + A’B, Carry = AB
- Sum = AB + A, Carry = A’B’
Answer: Sum = AB’ + A’B, Carry = AB
18. In the half adder circuit given figure if the inputs AB = 10 then
- X = 0; Y = 0
- X = 0; Y = 1
- X = 1; Y = 1
- X = 1; Y = 0
Answer: X = 1; Y = 0
19. In a look ahead carry adder, the carry of each stage (except the initial stage) is a function of
- carry propagate
- carry generate
- both
- none
Answer: both
20. BCD-adder requires — number of full adders
- one
- two
- three
- four
Answer: two
21. EX-3 adder requires — number of full adders
- one
- four
- three
- two
Answer: two
22. The — number of NAND gates are required to realize a half subtractor
- five
- six
- seven
- eight
Answer: seven
23. Full subtractor can be realized by using
- one half-subtractor and one OR gate
- two half-subtractor and one OR gate
- one half-subtractor and one AND gate
- two half-subtractor and one AND gate
Answer: two half-subtractor and one OR gate
24. BCD subtractor requires
- one parallel adder
- two parallel adders
- three parallel adders
- four parallel adders
Answer: four parallel adders
25. EX-3 subtractor can be implemented by using — number of parallel adders
- one
- two
- three
- four
Answer: two
26. Magnitude comparator is a circuit that compares
- magnitude of two numbers
- magnitude of three numbers
- magnitude of four numbers
- sign of two numbers
Answer: magnitude of two numbers
27. A decoder with n inputs produces maximum of — number of minterms
- 2n
- 2n – 1
- 2n – 1
- 2n
Answer: 2n
28. Any Boolean function can be implemented if it can be represented be — form
- SOP
- POS
- cannonical SOP
- cannonical POS
Answer: cannonical SOP
29. For economical realization decoder is used to realize a function which contains
- less number of don’t cares
- more number of don’t cares
- for any case
- none
Answer: less number of don’t cares
30. A 6-to-64 decoder can be obtained by cascading of…..
- four numbers 4-to-16 decoders and one 2 : 4 decoder
- five numbers 4-to-16 decoders
- three numbers 4-to-16 decoders and two numbers 2 : 4 decoder
- can not possible
Answer: four numbers 4-to-16 decoders and one 2 : 4 decoder
31. MUX is …… implementation
- AND-OR
- OR-AND
- NAND-OR
- NOR-AND
Answer: AND-OR
32. What is the number of inputs, outputs of a decoder that accepts 64 different input combinations?
- 5
- 6
- 64
- 8
Answer: 6
33. Which of the following statements refers to decoder?
- Only one output can be activated at any time
- Has more outputs than inputs
- Can be used as a BCD to 7 segment display interface
- All of the above
Answer: All of the above
34. Which of the following statements belongs to a MUX?
- Has more inputs than outputs
- Uses SELECT inputs
- Used in parallel to serial conversion
- All
Answer: All