Digital Electronics - Logic Gates

Exercise :: Logic Gates - General Questions

26. 

If the output of a three-input AND gate must be a logic LOW, what must the condition of the inputs be?

A. All inputs must be LOW.
B. All inputs must be HIGH.
C. At least one input must be LOW.
D. At least one input must be HIGH.

Answer: Option C

Explanation:

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27. 

Logically, the output of a NOR gate would have the same Boolean expression as a(n):

A. NAND gate immediately followed by an inverter
B. OR gate immediately followed by an inverter
C. AND gate immediately followed by an inverter
D. NOR gate immediately followed by an inverter

Answer: Option B

Explanation:

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28. 

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 dim indication on the logic probe indicates that the supply voltage is probably low.
B. The output of the gate appears to be open.
C. The dim indication is the result of a bad ground connection on the logic probe.
D. The gate is a tristate device.

Answer: Option B

Explanation:

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29. 

What is the Boolean expression for a three-input AND gate?

A. X = A + B + C
B. X = A · B · C
C. ABC
D. A $ B $ C

Answer: Option B

Explanation:

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30. 

Which of the following gates has the exact inverse output of the OR gate for all possible input combinations?

A. NOR
B. NOT
C. NAND
D. AND

Answer: Option A

Explanation:

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