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Transistor–transistor logic (TTL) is a class of digital circuits built from bipolar junction transistors (BJT) and resistors. It is called ''transistor–transistor logic'' because both the logic gating function (e.g., AND) and the amplifying function are performed by transistors (contrast with RTL and DTL). TTL is notable for being a widespread integrated circuit (IC) family used in many applications such as computers, industrial controls, test equipment and instrumentation, consumer electronics, synthesizers, etc. The designation ''TTL'' is sometimes used to mean TTL-compatible logic levels, even when not associated directly with TTL integrated circuits, for example as a label on the inputs and outputs of electronic instruments.〔 (Google preview ).〕 After their introduction in integrated circuit form in 1963 by Sylvania, TTL integrated circuits were manufactured by several semiconductor companies, with the 7400 series (also called 74xx) by Texas Instruments becoming particularly popular. TTL manufacturers offered a wide range of logic gate, flip-flops, counters, and other circuits. Several variations of the original bipolar TTL concept were developed, yielding circuits with higher speed or lower power dissipation to allow optimization of a design. TTL circuits simplified system design compared to earlier logic families, offering speed superior to resistor–transistor logic (RTL). The design of the input and outputs of TTL gates allowed many elements to be interconnected. TTL became the foundation of computers and other digital electronics. Even after much larger scale integrated circuits made multiple-circuit-board processors obsolete, TTL devices still found extensive use as the "glue" logic interfacing more densely integrated components. TTL devices were originally made in ceramic and plastic dual-in-line (DIP) packages, and flat-pack form. TTL chips are now also made in surface-mount packages. Successors to the original bipolar TTL logic often are interchangeable in function with the original circuits, but with improved speed or lower power dissipation. ==History== TTL was invented in 1961 by James L. Buie of TRW, "particularly suited to the newly developing integrated circuit design technology", and it was originally named ''transistor-coupled transistor logic'' (TCTL). The first commercial integrated-circuit TTL devices were manufactured by Sylvania in 1963, called the Sylvania Universal High-Level Logic family (SUHL).〔The Computer History Museum. (''1963 - Standard Logic Families Introduced.'' ) 2007. Retrieved 16 April 2008.〕 The Sylvania parts were used in the controls of the Phoenix missile.〔 TTL became popular with electronic systems designers after Texas Instruments introduced the 5400 series of ICs, with military temperature range, in 1964 and the later 7400 series, specified over a narrower range, and with inexpensive plastic packages in 1966. The Texas Instruments 7400 family became an industry standard. Compatible parts were made by Motorola, AMD, Fairchild, Intel, Intersil, Signetics, Mullard, Siemens, SGS-Thomson and National Semiconductor,〔Engineering Staff. ''The TTL Data Book for Design Engineers.'' 1st Ed. Dallas: Texas Instruments. 1973.〕 and many other companies, even in the Eastern Bloc (Soviet Union, GDR, Poland, Bulgaria). Not only did others make compatible TTL parts, but compatible parts were made using many other circuit technologies as well. At least one manufacturer, IBM, produced non-compatible TTL circuits for its own use; IBM used the technology in the IBM System/38, IBM 4300, and IBM 3081.〔, p. 5.〕 The term "TTL" is applied to many successive generations of bipolar logic, with gradual improvements in speed and power consumption over about two decades. The most recently introduced family 74Fxx is still sold today, and was widely used into the late 90s. 74AS/ALS Advanced Schottky, was introduced in 1985.〔Texas Instruments. (''Advanced Schottky Family.'' ) 1985. Retrieved 17 September 2008.〕 As of 2008, Texas Instruments continues to supply the more general-purpose chips in numerous obsolete technology families, albeit at increased prices. Typically, TTL chips integrate no more than a few hundred transistors each. Functions within a single package generally range from a few logic gates to a microprocessor bit-slice. TTL also became important because its low cost made digital techniques economically practical for tasks previously done by analog methods. The Kenbak-1, ancestor to the first personal computers, uses TTL for its CPU instead of a microprocessor chip, which was not available in 1971.〔Klein, E. (''Kenbak-1.'' ) Vintage-Computer.com. 2008.〕 The 1973 Xerox Alto and 1981 Star workstations, which introduced the graphical user interface, use TTL circuits integrated at the level of ALUs and bitslices, respectively. Most computers used TTL-compatible "glue logic" between larger chips well into the 1990s. Until the advent of programmable logic, discrete bipolar logic was used to prototype and emulate microarchitectures under development. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Transistor–transistor logic」の詳細全文を読む スポンサード リンク
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