Difficulty: Easy
Correct Answer: No signal must pass through more than two gates, not including inverters.
Explanation:
Introduction / Context:
Sum-of-products (SOP) expresses a Boolean function as an OR of product terms. In a two-level realization, each product term is an AND of literals, and the final stage is a single OR combining those terms. This structure is widely used in PLDs and minimized gate designs.
Given Data / Assumptions:
Concept / Approach:
In a canonical two-level SOP implementation, any input signal traverses at most an AND gate and then an OR gate to reach the output. This bounded depth is advantageous for timing predictability and is foundational in programmable logic device architectures.
Step-by-Step Solution:
Express F as F = P1 + P2 + ... + Pk where each Pi is a product (AND) of literals.Route each input to the required AND gate(s) to form the product terms.Feed the outputs of all AND gates into a single OR gate.Hence, each signal path goes through at most two logic gates (AND then OR).
Verification / Alternative check:
This property underlies classic two-level minimization methods (K-maps, Quine–McCluskey) and the structure of sum-of-products implementations in PLDs.
Why Other Options Are Wrong:
Common Pitfalls:
Counting inverters as logic levels, or assuming a specific delay advantage without considering gate fan-in and loading.
Final Answer:
No signal must pass through more than two gates, not including inverters.
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