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Digital logic fundamentals: Is it true that both OR gates and AND gates are limited to having only two inputs each?

Difficulty: Easy

Correct Answer: False

Explanation:


Introduction / Context:
This question tests knowledge about the scalability of basic logic gates. While introductory textbooks often show OR and AND gates with two inputs, in practice digital logic gates can have multiple inputs. Understanding this clears up a common beginner misconception.


Given Data / Assumptions:

  • Logic families include TTL, CMOS, and ECL.
  • OR and AND gates are basic Boolean operators.
  • Nothing inherently restricts them to two inputs.


Concept / Approach:
Boolean logic allows OR and AND with any number of inputs: A + B + C, or A * B * C, etc. In hardware, ICs are fabricated with 2-input, 3-input, 4-input, or even 8-input gates. Thus, the statement that they can have 'only two inputs' is false.


Step-by-Step Solution:

Recall that OR is true if any input is true; AND is true if all inputs are true.For 2 inputs: Y = A + B (OR), Y = A * B (AND).For 3 inputs: Y = A + B + C (OR), Y = A * B * C (AND).Logic ICs like 7432 (quad 2-input OR) and 4072 (dual 4-input OR) prove higher input counts exist.


Verification / Alternative check:
Datasheets for TTL families (e.g., 74LS21: dual 4-input AND) confirm multi-input gates are widely available.


Why Other Options Are Wrong:

'True': incorrect, as many-input gates exist.'Only for TTL' or 'Depends on implementation': misleading, because TTL also supports multi-input gates.'True for AND but not for OR': both support multiple inputs.


Common Pitfalls:

Believing textbooks that only show 2-input gates means only 2-input exist.Confusing conceptual representation with hardware implementation limits.


Final Answer:

False
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