7400 seriesThe series logic TTL chips spawned a series of other derivative logic families offering slightly different characteristics: high speed, low power, etc. However the standard parameters remained the same: logic function a and a 74LS16 had the same function; they were pin compatible, etc. The series TTL chips remained in use for many years. They have long been superseded by other 74xx00 logic families, but they have been so successful that the basic concept has remained the same. Some of the main or highlight features and specifications for the series logic family are detailed below:. The logic series of ICs were fabricated using bipolar transistor technology and this gave its name to the logic technology, TTL standing for transistor-transistor logic. The series TTL ran from a nominal 5 Volt supply line and as a result of its popularity the 5 V line became standard for logic chips for many years, only changing when power restrictions and smaller feature sizes on chips as a result of higher integration and new processes forced the operating voltage down. Although launched in the mids the series became the main standard set of logic widely used in electronic digital circuits. There were earlier TTL series of chips. With their increasing popularity, the cost of the chips came down. Initial offerings cost many dollars each, but over time as production techniques matured and quantities rose vastly, some series chips could be bought for a few cents each. From the circuit diagram the basic blocks of this simple series IC can be easily seen. The input stage of the NAND gate is a multi-emitter transistor. This takes the inputs and provides the required logic. The next stage provides the required phase and drive for the final stage which is the standard totem pole output. It comprises two transistors and enables very fast switching times to be achieved. In this arrangement either Q1 or Q2 conducts dependent upon the complementary logic status of the inputs. The diode D1 ensures that Q2 is able to turn off rapidly when required. In this way external loads can be connected between the output, i. This has many applications including driving indicator lamps. However the speed of switching is much slower and dependent upon external influences. It is able to provide the high and low of a normal output. It is also possible to disable the output so it has no effect on the line being driven - in this state it is open circuit or floating. In order to be able to select this state, an additional "enable" input is required on the chip. To achieve the tri-state situation, the internal circuitry is arranged so that both transistors in the totem-pole output can be tuned off at the same time. Supplier Directory For everything from distribution to test equipment, components and more, our directory covers it. Featured articles.
Tomma 7400 SERIES
The series of integrated circuits ICs are the most popular logic families. The series contains hundreds of devices that provide everything from basic logic gatesflip-flopsand counters, to special purpose bus transceivers and arithmetic logic units ALU. Specific functions are described in a list of series integrated circuits. Some TTL logic parts were made with an extended military-specification temperature range. These parts are prefixed with 54 instead of 74 in the part number. A short-lived 64 prefix on Texas Instruments parts indicated an industrial temperature range [ citation needed ] ; this prefix had been dropped from the TI literature by Since the s, new product families have been released to replace the original series. Today, surface-mounted CMOS versions of the series are used in various applications in electronics and for glue logic in computers and industrial electronics. They are useful for rapid breadboard -prototyping and for education and remain available from most manufacturers. The fastest types and very low voltage versions are typically surface-mount only, however. Additional characters in a part number identify the package and other variations. Unlike the older resistor-transistor logic integrated circuits, bipolar TTL gates were unsuitable to be used as analog devices, providing low gain, poor stability, and low input impedance. Inverting gates could be cascaded as a ring oscillatoruseful for purposes where high stability was not required. Although the series was the first de facto industry standard TTL logic family i. The quad NAND gate was the first product in the series, introduced by Texas Instruments in a military grade metal flat package W in October The pin assignment of this early series differed from the de facto standard set by the later series in DIP packages in particular, ground was connected to pin 11 and the power supply to pin 4, compared to pins 7 and 14 for DIP packages. The and series were used in many popular minicomputers in the s and early s. Intypical quantity-one pricing for the SN military grade, in ceramic welded flat-pack was around 22 USD. Originally the bipolar circuits provided higher speed but consumed more power than the competing series of CMOS devices. Milspec -rated devices for use in extended temperature conditions are available as the series. Texas Instruments also manufactured radiation-hardened devices with the prefix RSNand the company offered beam-lead bare dies for integration into hybrid circuits with a BL prefix designation. While companies such as Mullard listed series compatible parts in data sheets,  by there was no mention of the family in the Texas Instruments TTL Data Book. Some companies have also offered industrial extended temperature range variants using the regular series part numbers with a prefix or suffix to indicate the temperature grade. As integrated circuits in the series were made in different technologies, usually compatibility was retained with the original TTL logic levels and power supply voltages. Over 40 different logic subfamilies use this standardized part number scheme. TTL has the input high level above 2. The 74H family is the same basic design as the family with resistor values reduced. The 74H family provided a number of unique devices for CPU designs in the s. Many designers of military and aerospace equipment used this family over a long period and as they need exact replacements, this family is still produced by Lansdale Semiconductor. The 74S family, using Schottky circuitry, uses more power than the 74, but is faster.
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