Digital Electronics Combinational Logic Circuits Questions and Answers

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Q21
Which of the following expressions is in the sum-of-products form?
  • A (A + B)(C + D)
  • B (AB)(CD)
  • C AB(CD)
  • D AB + CD
Answer: Option D
Q22
A decoder can be used as a demultiplexer by ________.
  • A tying all enable pins LOW
  • B tying all data-select lines LOW
  • C tying all data-select lines HIGH
  • D using the input lines for data selection and an enable line for data input
Answer: Option D
Q23
How many 4-bit parallel adders would be required to add two binary numbers each representing decimal numbers up through 30010?
  • A 1
  • B 2
  • C 3
  • D 4
Answer: Option C
Q24
Which statement below best describes a Karnaugh map?
  • A A Karnaugh map can be used to replace Boolean rules.
  • B The Karnaugh map eliminates the need for using NAND and NOR gates.
  • C Variable complements can be eliminated by using Karnaugh maps.
  • D Karnaugh maps provide a visual approach to simplifying Boolean expressions.
Answer: Option D
Q25
A certain BCD-to-decimal decoder has active-HIGH inputs and active-LOW outputs. Which output goes LOW when the inputs are 1001?
  • A 0
  • B 3
  • C 9
  • D None. All outputs are HIGH.
Answer: Option C
Q26
The design concept of using building blocks of circuits in a PLD program is called a(n):
  • A hierarchical design.
  • B architectural design.
  • C digital design.
  • D verilog.
Answer: Option A
Q27
When adding an even parity bit to the code 110010, the result is ________.
  • A 1110010
  • B 1111001
  • C 110010
  • D 001101
Answer: Option A
Q28
Which of the following combinations of logic gates can decode binary 1101?
  • A One 4-input AND gate
  • B One 4-input AND gate, one OR gate
  • C One 4-input NAND gate, one inverter
  • D One 4-input AND gate, one inverter
Answer: Option D
Q29
What is the indication of a short to ground in the output of a driving gate?
  • A Only the output of the defective gate is affected.
  • B There is a signal loss to all load gates.
  • C The node may be stuck in either the HIGH or the LOW state.
  • D The affected node will be stuck in the HIGH state.
Answer: Option B
Q30
How many outputs would two 8-line-to-3-line encoders, expanded to a 16-line-to-4-line encoder, have?
  • A 3
  • B 4
  • C 5
  • D 6
Answer: Option B

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