Transistor-Transistor Logic

(TTL) A common semiconductor technology for building discrete

digital logic integrated circuits. It originated from TexasInstruments in 1965.

There have been several series of TTL logic:

7400: 10 ns propagation time, 10 mW/gate power consumption,

obsolete;

74L00: Low power: higher resistances, less dissipation

(1 mW), longer propagation time (30 ns);

74H00: High power: lower resistances, more dissipation: less

sensitivity for noise;

74S00: Schottky-clamped: faster switching (3 ns, 19 mW) by

using Schottky diodes to prevent the transistors from

saturation;

74LS00: Low power, Schottky-clamped (10 ns, 2 mW);

74AS00: Advanced Schottky: faster switching, less

dissipation, (1.5 ns, 10 mW);

74ALS00: Advanced Low power Schottky (4 ns, 1.3 mW).

For each 74xxx family there is a corresponding 54xxx family.

The 74 series are specified for operation at 0 - 70 C whereas

the 54 (military) series can operate at -55 - 125 C

See also CMOS, ECL.