Common TTL Series Identification — Which family code is most prevalent? Among the listed options, select the designation that refers to the classic, widely used TTL logic IC series.

Introduction / Context:
The “7400” designation identifies the ubiquitous TTL logic family that defined small-scale and medium-scale integration for decades. Many subfamilies (LS, ALS, S, AS, H, F, etc.) expand on the basic 7400 lineage, each optimizing for speed, power, or drive.

Given Data / Assumptions:

• Standard TTL parts are commonly denoted 74xx for commercial temperature ranges (and 54xx for military).
• Examples: 7400 (quad NAND), 74138 (3-to-8 decoder), 7474 (dual D flip-flop).
• Other strings in the options are not family designations.

Concept / Approach:
Recognize that “7400” is a canonical family marker for TTL logic ICs. Terms like “E-MOSFET” describe device physics, not a TTL series. “AC00” refers to an advanced CMOS (74AC) variant—not TTL. “quad” describes a package function count, not a series.

Step-by-Step Solution:
Identify a family indicator among options.Match to standard TTL naming → “7400.”Exclude descriptive or CMOS-family terms.

Verification / Alternative check:
Datasheets and catalogs list 74xx series parts as TTL; 74HC/AC families are CMOS with TTL-compatible inputs but are distinct from original TTL.

Why Other Options Are Wrong:

• E-MOSFET: Device type, not a TTL family.
• quad: Merely indicates four gates/units; not a series.
• AC00: Part of 74AC CMOS family, not TTL.

Common Pitfalls:
Assuming all “74xx” parts are TTL; some modern “74xx” are CMOS (HC/HCT/AC/LCX). Check family suffixes.

Final Answer:
7400