TTL families comparison: among the listed transistor–transistor logic (TTL) subfamilies, which is generally the fastest due to reduced storage delay?

Introduction / Context:
TTL has multiple subfamilies optimized for speed, power, or noise immunity. Speed improvements often come from device physics and circuit tricks that shorten transistor saturation/storage delays. Schottky TTL integrates Schottky diodes to prevent deep saturation, achieving faster switching.

Given Data / Assumptions:

• We compare general subfamilies: standard, high-speed, Schottky, and low-speed TTL.
• Process variations aside, Schottky clamping reduces storage time.
• We ignore later advanced variants (e.g., ALS/AS/FAST) not listed in the options.

Concept / Approach:
Schottky diodes across base–collector junctions keep transistors out of deep saturation, minimizing charge storage that must be removed during turn-off. This directly lowers propagation delay compared to standard/high-speed TTL without Schottky clamps.

Step-by-Step Solution:

Verification / Alternative check:
Datasheets show lower typical propagation delays for S-TTL than standard or generic high-speed TTL families of the same era.

Why Other Options Are Wrong:

Common Pitfalls:
Confusing Schottky TTL with CMOS families; CMOS speed depends on different factors and is not part of this comparison.

Final Answer:
schottky TTL