Description of TTL, ECL and CMOS Glue Logic Families

There are additional signaling types; however, many do not exist as a logic family.
FPGA's, Memory devices or other high-end logic devices may use different signaling levels.
The IC bus page list the addition digital interface levels.

This is a listing of TTL, ECL and CMOS Glue Logic Families, with a short description of how they differ from one another. The 74xx families are shown above, but the 54xx families also applies. The 74 designates commercial temperature ranges and the 54 designates operation at Military temperature ranges. Component manufacturers may be found by clicking the Components icons at the bottom of the page. In general, none of the logic families listed above will operate with any other logic family, the voltage thresholds are different for each logic family.
Refer to the Logic Family Voltage Translation page for interfacing techniques between logic families. Back to the Logic Design Page

The CMOS [74C] families listed under the 'true' TTL header are CMOS devices, but not 'true' CMOS devices. They're more CMOS than TTL but don't switch at CMOS levels, designed to work with TTL devices. To be considered a CMOS [54C] logic device the entire internal structure needs to be CMOS, otherwise the component would draw current like a TTL IC.

Many of the earlier logic families are obsolete or at least in decline. Some families are still only in production to support legacy programs.
The oldest of the logic families include the 'L', S, LS, C, and HC glue logic families.

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