Digital Electronics Combinational Logic Circuits Questions and Answers

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Q11
Which of the following expressions is in the product-of-sums form?
  • A (A + B)(C + D)
  • B (AB)(CD)
  • C AB(CD)
  • D AB + CD
Answer: Option A
Q12
Which of the following is an important feature of the sum-of-products form of expressions?
  • A All logic circuits are reduced to nothing more than simple AND and OR operations.
  • B The delay times are greatly reduced over other forms.
  • C No signal must pass through more than two gates, not including inverters.
  • D The maximum number of gates that any signal must pass through is reduced by a factor of two.
Answer: Option A
Q13
An output gate is connected to four input gates; the circuit does not function. Preliminary tests with the DMM indicate that the power is applied; scope tests show that the primary input gate has a pulsing signal, while the interconnecting node has no signal. The four load gates are all on different ICs. Which instrument will best help isolate the problem?
  • A Current tracer
  • B Logic probe
  • C Oscilloscope
  • D Logic analyzer
Answer: Option A
Q14
The binary numbers A = 1100 and B = 1001 are applied to the inputs of a comparator. What are the output levels?
  • A A > B = 1, A < B = 0, A < B = 1
  • B A > B = 0, A < B = 1, A = B = 0
  • C A > B = 1, A < B = 0, A = B = 0
  • D A > B = 0, A < B = 1, A = B = 1
Answer: Option C
Q15
A logic probe is placed on the output of a gate and the display indicator is dim. A pulser is used on each of the input terminals, but the output indication does not change. What is wrong?
  • A The output of the gate appears to be open.
  • B The dim indication on the logic probe indicates that the supply voltage is probably low.
  • C The dim indication is a result of a bad ground connection on the logic probe.
  • D The gate may be a tristate device.
Answer: Option A
Q16
Each &quot;1&quot; entry in a K-map square represents:
  • A a HIGH for each input truth table condition that produces a HIGH output.
  • B a HIGH output on the truth table for all LOW input combinations.
  • C a LOW output for all possible HIGH input conditions.
  • D a DON'T CARE condition for all possible input truth table combinations.
Answer: Option A
Q17
Looping on a K-map always results in the elimination of:
  • A variables within the loop that appear only in their complemented form.
  • B variables that remain unchanged within the loop.
  • C variables within the loop that appear in both complemented and uncomplemented form.
  • D variables within the loop that appear only in their uncomplemented form.
Answer: Option C
Q18
What will a design engineer do after he/she is satisfied that the design will work?
  • A Put it in a flow chart
  • B Program a chip and test it
  • C Give the design to a technician to verify the design
  • D Perform a vector test
Answer: Option B
Q19
What is the indication of a short on the input of a load gate?
  • A Only the output of the defective gate is affected.
  • B There is a signal loss to all gates on the node.
  • C The affected node will be stuck in the LOW state.
  • D There is a signal loss to all gates on the node, and the affected node will be stuck in the LOW state.
Answer: Option D
Q20
In HDL, LITERALS is/are:
  • A digital systems.
  • B scalars.
  • C binary coded decimals.
  • D a numbering system.
Answer: Option B

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