Computer Hardware Terms, Glossary and Dictionary

Transistor-to-Transistor Logic (TTL) is a digital logic design in which bipolar transistors act on direct-current pulses. Many TTL logic gates are typically fabricated onto a single integrated circuit (IC). TTL ICs usually have four-digit numbers beginning with 74 or 54. A TTL device employs transistors with multiple emitters in gates having more than one input. TTL is characterized by high switching speed (in some cases upwards of 125 MHz), and relative immunity to noise. Its principle drawback is the fact that circuits using TTL draw more current than equivalent circuits using metal oxide semiconductor (MOS) logic. Low-current TTL devices are available, but the reduced current demand comes at the expense of some operating speed.

Related Terms

TTL: Transistor-to-Transistor Logic