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