Difficulty: Easy
Correct Answer: AS-TTL
Explanation:
Introduction / Context:
Classic TTL families evolved to improve speed and reduce power. Schottky clamping prevents deep saturation, improving switching time; later “Advanced Schottky” refinements push speed further. This question compares well-known TTL derivatives and HCMOS on maximum practical clock frequency (ignoring ECL, which is not listed here).
Given Data / Assumptions:
Concept / Approach:
Advanced Schottky TTL reduces storage delay and optimizes device structures/resistors for improved speed relative to earlier TTL lines. Although modern CMOS in deep-submicron processes is very fast, traditional family-to-family comparisons (same era) place 74ASXX at the top among the given TTL variants for max clock rate.
Step-by-Step Solution:
Verification / Alternative check:
Historic datasheets show lower t_pd for 74AS vs. 74S and 74H series under comparable loading.
Why Other Options Are Wrong:
Common Pitfalls:
Confusing modern high-speed CMOS ASICs or FPGAs with classic HCMOS logic families.
Final Answer:
AS-TTL
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