Editing Transistor–transistor logic (section)

==History==
[[File:TTL Clock.jpg|thumb|upright|A real-time clock built of TTL chips around 1979]]

TTL was invented in 1961 by [[James L. Buie]] of [[TRW Inc.|TRW]], which declared it "particularly suited to the newly developing integrated circuit design technology." The original name for TTL was ''transistor-coupled transistor logic'' (TCTL).<ref>{{cite patent | country=US | number=3283170 | title=Coupling transistor logic and other circuits | gdate=1966-11-01 | fdate=1961-09-08 | inventor1-first=James L. |inventor1-last=Buie | assign1=TRW Semiconductors, Inc.}}</ref> The first commercial integrated-circuit TTL devices were manufactured by Sylvania in 1963, called the Sylvania Universal High-Level Logic family (SUHL).<ref name="The Computer History Museum 2007">{{cite web |publisher=The Computer History Museum |url=http://www.computerhistory.org/semiconductor/timeline/1963-TTL.html |title=1963: Standard Logic Families Introduced |date=2007 |work=Timeline}}</ref> The Sylvania parts were used in the controls of the [[Phoenix missile]].<ref name="The Computer History Museum 2007"/> 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.<ref>{{citation |first=Bo |last=Lojek |title=History of semiconductor engineering |publisher=Springer |year=2006 |isbn=3-540-34257-5 |pages=212–215}}</ref>

The Texas Instruments 7400 family became an industry standard. Compatible parts were made by [[Motorola]], [[AMD]], [[Fairchild Semiconductor|Fairchild]], [[Intel]], [[Intersil]], [[Signetics]], [[Mullard]], [[Siemens]], [[SGS-Thomson]], [[RIFA (manufacturer)|Rifa]], [[National Semiconductor]],<ref>{{cite book |author=Engineering Staff |title=The TTL Data Book for Design Engineers |edition=1st  |location=Dallas |publisher=Texas Instruments |date=1973 |oclc=6908409}}</ref><ref>{{citation |editor-first=L. W. |editor-last=Turner |title=Electronics Engineer's Reference Book |edition=4th |publisher=Newnes-Butterworth |location=London |year=1976 |isbn=0408001682}}</ref> and many other companies, even in the Eastern Bloc (Soviet Union, GDR, Poland, Czechoslovakia, Hungary, Romania — for details see [[7400 series#Second sources from Europe and Eastern Bloc|7400 series]]). 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]].<ref>{{citation |last1=Pittler |first1=M. S. |last2=Powers |first2=D. M. |last3=Schnabel |first3=D. L. |url=http://www.research.ibm.com/journal/rd/261/ibmrd2601B.pdf |archive-url=https://web.archive.org/web/20110604200220/http://www.research.ibm.com/journal/rd/261/ibmrd2601B.pdf |archive-date=2011-06-04 |url-status=live |title=System development and technology aspects of the IBM 3081 Processor Complex |journal=IBM Journal of Research and Development |volume=26 |date=1982 |issue=1 |pages=2–11 |doi=10.1147/rd.261.0002}}, p. 5.</ref>

The term "TTL" is applied to many successive generations of [[BJT|bipolar]] logic, with gradual improvements in speed and power consumption over about two decades. The most recently introduced family 74Fxx is still sold today (as of 2019), and was widely used into the late 90s. 74AS/ALS Advanced Schottky was introduced in 1985.<ref>{{cite web |publisher=Texas Instruments |url=http://focus.ti.com/lit/an/sdaa010/sdaa010.pdf |archive-url=https://web.archive.org/web/20110604174329/http://focus.ti.com/lit/an/sdaa010/sdaa010.pdf |archive-date=2011-06-04 |url-status=live |title=Advanced Schottky Family |id=SDAA010 |date=1985}}</ref> 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 gate]]s 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.<ref>{{citation |author1-link=Don Lancaster |last=Lancaster |first=D. |title=TTL Cookbook |location=Indianapolis |publisher=Howard W. Sams and Co. |year=1975 |isbn=0-672-21035-5 |page=[https://archive.org/details/ttlcookbook00lanc/page/ preface] |url=https://archive.org/details/ttlcookbook00lanc/page/ }}</ref>

The [[Kenbak-1]], ancestor of the first [[personal computer]]s, used TTL for its [[Central processing unit|CPU]] instead of a [[microprocessor]] chip, which was not available in 1971.<ref>{{cite web |last=Klein |first=E. |url=http://www.vintage-computer.com/machines.php?kenbak1 |title=Kenbak-1 |publisher=Vintage-Computer.com |date=2008}}</ref> The [[Datapoint 2200]] from 1970 used TTL components for its CPU and was the basis for the [[Intel 8008|8008]] and later the [[x86]] instruction set.<ref name="wood">{{cite news |first=Lamont |last=Wood  |url=http://www.computerworld.com/action/article.do?command=printArticleBasic&articleId=9111341 |title=Forgotten PC history: The true origins of the personal computer |archive-url=https://web.archive.org/web/20080814215757/http://www.computerworld.com/action/article.do?command=printArticleBasic&articleId=9111341 |archive-date=2008-08-14 |newspaper=Computerworld |date=8 August 2008}}</ref> The 1973 [[Xerox Alto]] and 1981 [[Xerox Star|Star]] workstations, which introduced the [[graphical user interface]], used TTL circuits integrated at the level of [[arithmetic logic unit]]s (ALUs) and bitslices, respectively.  Most computers used TTL-compatible "[[glue logic]]"  between larger chips well into the 1990s. Until the advent of [[Programmable logic device|programmable logic]], discrete bipolar logic was used to prototype and [[hardware emulation|emulate]] [[microarchitecture]]s under development.