The Kenbak-1 , ancestor of the first personal computers , used TTL for its CPU instead of a microprocessor chip, which was not available in Standard TTL circuits operate with a 5- volt power supply. TTL inputs are sometimes simply left floating to provide a logical “1”, though this usage is not recommended. The resistor R 3 does not increase the output resistance since it is connected in the V 3 collector and its influence is compensated by the negative feedback. A common variation omits the collector resistor of the output transistor, making an open-collector output. The term “TTL” is applied to many successive generations of bipolar logic, with gradual improvements in speed and power consumption over about two decades.

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This page was last edited on 20 Decemberat Some advantage of the simple output stage is the high voltage level up to V CC of the output logical “1” when the output is not loaded. Beam-lead chip dies without packages were made for assembly into larger arrays as hybrid integrated circuits.

Solved: OK to put in 5V TTL into a LVTTL devices – Discussion Forums – National Instruments

Successive generations of technology produced compatible parts with improved power consumption or switching speed, or both. You might want to consider what happens if a 3. Open-collector outputs of some gates have a higher maximum voltage, such as 15V for the[16] useful when driving other than TTL loads. TTL also became important because its low cost made digital techniques economically practical for tasks previously done by analog methods.


The output can be erratic when the input is in this range. In the middle of the transition, the resistor R 3 limits the current flowing directly through the series connected transistor V 3diode V 5 and transistor V 4 that are all conducting.

These pulses can couple in unexpected ways between multiple integrated circuit packages, resulting in reduced noise margin and lower performance. To solve the problem with the high output resistance of the simple output stage the second schematic adds lvttk this a “totem-pole” ” push—pull ” output. Transistor—transistor logic TTL is a logic family built from bipolar junction transistors.

TTL chips are now also made in surface-mount packages. Epoxy plastic PDIP packages were often used for commerical temperature range components, while pvttl packages CDIP were used for military temperature range parts.

Digital I/O

Retrieved from ” https: TTL is particularly well suited to bipolar integrated circuits because additional inputs to a gate merely required additional emitters on a shared base region of the input transistor. TTL became the foundation of computers and other digital electronics.

Views Read Edit View history. The Kenbak-1ancestor of the first personal computersused TTL for its CPU instead of a microprocessor chip, which was not available in The output stage of the most common TTL gates is specified to function correctly when driving up to 10 standard input stages a fanout of lvytl It limits the number of inputs that can be connected the fanout. An input logical zero. TTL systems usually have a decoupling capacitor for every one or two IC kvttl, so that a current pulse from one TTL chip does not momentarily reduce the supply voltage to another.


Webarchive template wayback links All articles with vague or ambiguous time Vague or ambiguous time from September Commons category link is on Wikidata Wikipedia articles with GND identifiers. Inputs both logical ones. This drawback is usually overcome by buffering the outputs with special line-driver devices where signals need to be sent through cables.

In the case of NAND inputs, the inputs are the emitters of multiple-emitter transistorsfunctionally equivalent to multiple transistors where the bases and collectors are tied together. If individually packaged transistors were used, the cost of all the transistors would discourage one from using such an input structure.

Transistor–transistor logic

The second series combination has the higher threshold voltage, so no current flows through it, i. Post as a guest Name. Retrieved 27 October Digital Logic Gates Part-V. Two circuit board units off the same assembly line on different successive days or weeks might have a different mix of brands of chips in the same positions on the board; repair is possible with chips manufactured years later than original components.

TTL inputs are the emitters of bipolar transistors. It pulls up the V 5 cathode and cuts-off the diode.