7400-series integrated circuits

The 7400 series is a popular logic family of transistor–transistor logic integrated circuits.
In 1964, Texas Instruments introduced the SN5400 series of logic chips, in a ceramic semiconductor package. A low-cost plastic package SN7400 series was introduced in 1966 which quickly gained over 50% of the logic chip market, and eventually becoming de facto standardized electronic components. Since the introduction of the original bipolar-transistor TTL parts, pin-compatible parts were introduced with such features as low power CMOS technology and lower supply voltages. Surface mount packages exist for several popular logic family functions.

Overview

The 7400 series contains hundreds of devices that provide everything from basic logic gates, flip-flops, and counters, to special purpose bus transceivers and arithmetic logic units. Specific functions are described in a list of 7400 series integrated circuits. Some TTL parts were made with an extended military-specification temperature range. These parts are prefixed with 54 instead of 74 in the part number. The less-common 64 and 84 prefixes on Texas Instruments parts indicated an industrial temperature range. Since the 1970s, new product families have been released to replace the original 7400 series. More recent TTL-compatible logic families were manufactured using CMOS or BiCMOS technology rather than TTL.

Prefix	Name	Temperature range	Remarks
54	Military	−55 °C to +125 °C
64	Industrial	−40 °C to +85 °C	rare
74	Commercial	0 °C to +70 °C	most common
84	Industrial	−25 °C to +85 °C	rare

Today, surface-mounted CMOS versions of the 7400 series are used in various applications in electronics and for glue logic in computers and industrial electronics. The original through-hole devices in dual in-line packages were the mainstay of the industry for many decades. 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.
The first part number in the series, the 7400, is a 14-pin IC containing four two-input NAND gates. Each gate uses two input pins and one output pin, with the remaining two pins being power and ground. This part was made in various through-hole and surface-mount packages, including flat pack and plastic/ceramic dual in-line. 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. Special-purpose TTL devices were used to provide interface functions such as Schmitt triggers or monostable multivibrator timing circuits. Inverting gates could be cascaded as a ring oscillator, useful for purposes where high stability was not required.

History

Although the 7400 series was the first de facto industry standard TTL logic family, there were earlier TTL logic families such as:

Sylvania Universal High-level Logic in 1963
Motorola MC4000 MTTL
National Semiconductor DM8000
Fairchild 9300 series
Signetics 8200 and 8T00

The 7400 quad 2-input NAND gate was the first product in the series, introduced by Texas Instruments in a military grade metal flat package in October 1964. The pin assignment of this early series differed from the de facto standard set by the later series in DIP packages. The extremely popular commercial grade plastic DIP followed in the third quarter of 1966.
The 5400 and 7400 series were used in many popular minicomputers in the 1970s and early 1980s. Some models of the DEC PDP-series "minis" used the 74181 ALU as the main computing element in the CPU. Other examples were the Data General Nova series and Hewlett-Packard 21MX, 1000, and 3000 series.
In 1965, typical quantity-one pricing for the SN5400 was around 22 USD. As of 2007, individual commercial-grade chips in molded epoxy packages can be purchased for approximately US$0.25 each, depending on the particular chip.

Families

7400 series parts were constructed using bipolar junction transistors, forming what is referred to as transistor–transistor logic or TTL. Newer series, more or less compatible in function and logic level with the original parts, use CMOS technology or a combination of the two. Originally the bipolar circuits provided higher speed but consumed more power than the competing 4000 series of CMOS devices. Bipolar devices are also limited to a fixed power-supply voltage, typically 5 V, while CMOS parts often support a range of supply voltages.
Milspec-rated devices for use in extended temperature conditions are available as the 5400 series. Texas Instruments also manufactured radiation-hardened devices with the prefix RSN, and the company offered beam-lead bare dies for integration into hybrid circuits with a BL prefix designation.
Regular-speed TTL parts were also available for a time in the 6400 series these had an extended industrial temperature range of −40 °C to +85 °C. While companies such as Mullard listed 6400-series compatible parts in 1970 data sheets, by 1973 there was no mention of the 6400 family in the Texas Instruments TTL Data Book. Texas Instruments brought back the 6400 series in 1989 for the SN64BCT540. The SN64BCTxxx series is still in production as of 2023. Some companies have also offered industrial extended temperature range variants using the regular 7400-series part numbers with a prefix or suffix to indicate the temperature grade.
As integrated circuits in the 7400 series were made in different technologies, usually compatibility was retained with the original TTL logic levels and power-supply voltages. An integrated circuit made in CMOS is not a TTL chip, since it uses field-effect transistors and not bipolar junction transistors, but similar part numbers are retained to identify similar logic functions and electrical compatibility in the different subfamilies.
Over 40 different logic subfamilies use this standardized part number scheme. The headings in the following table are: V_cc power-supply voltage; t_pd maximum gate delay; I_OL maximum output current at low level; I_OH maximum output current at high level; t_pd, I_OL, and I_OH apply to most gates in a given family. Driver or buffer gates have higher output currents.
Many parts in the CMOS HC, AC, AHC, and VHC families are also offered in "T" versions which have input thresholds that are compatible with both TTL and 3.3 V CMOS signals. The non-T parts have conventional CMOS input thresholds, which are more restrictive than TTL thresholds. Typically, CMOS input thresholds require high-level signals to be at least 70% of Vcc and low-level signals to be at most 30% of Vcc.
The 74H family is the same basic design as the 7400 family with resistor values reduced. This reduced the typical propagation delay from 9 ns to 6 ns but increased the power consumption. The 74H family provided a number of unique devices for CPU designs in the 1970s. 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. The 74LS family of ICs is a lower-power version of the 74S family, with slightly higher speed but lower power dissipation than the original 74 family; it became the most popular variant once it was widely available. Many 74LS ICs can be found in microcomputers and digital consumer electronics manufactured in the 1980s and early 1990s.
The 74F family was introduced by Fairchild Semiconductor and adopted by other manufacturers; it is faster than the 74, 74LS and 74S families.
Through the late 1980s and 1990s newer versions of this family were introduced to support the lower operating voltages used in newer CPU devices.

Part numbering

Part number schemes varied by manufacturer. The part numbers for 7400-series logic devices often use the following designators:

Often first, a two or three letter prefix, denoting the manufacturer and flow class of the device. These codes are no longer closely associated with a single manufacturer, for example, Fairchild Semiconductor manufactures parts with MM and DM prefixes, and no prefixes. Examples:
* SN: Texas Instruments using a commercial processing
* SNV: Texas Instruments using military processing
* M: ST Microelectronics
* DM: National Semiconductor
* UT: Cobham PLC
* SG: Sylvania
* RD: RIFA AB
Two digits for temperature range. Examples:
* 54: military temperature range
* 64: short-lived historical series with intermediate "industrial" temperature range
* 74: commercial temperature range device
Zero to four letters denoting the logic subfamily. Examples:
* zero letters: basic bipolar TTL
* LS: low power Schottky
* HCT: High-speed CMOS compatible with TTL
Two or more arbitrarily assigned digits that identify the function of the device. There are hundreds of different devices in each family.
Additional suffix letters and numbers may be appended to denote the package type, quality grade, or other information, but this varies widely by manufacturer.

For example, "SN5400N" signifies that the part is a 7400-series IC probably manufactured by Texas Instruments using commercial processing, is of the military temperature rating, and is of the TTL family, its function being the quad 2-input NAND gate implemented in a plastic through-hole DIP package.
Many logic families maintain a consistent use of the device numbers as an aid to designers. Often a part from a different 74x00 subfamily could be substituted in a circuit, with the same function and pin-out yet more appropriate characteristics for an application, which was a large part of the appeal of the 74C00 series over the competing CD4000B series, for example. But there are a few exceptions where incompatibilities across the subfamilies occurred, such as:

some flat-pack devices and surface-mount devices,
some of the faster CMOS series,
a few low-power TTL devices have a different pin-out than the regular series part.
five versions of the 74x54, namely 7454, 7454W, 74H54, 74L54W and 74L54N/74LS54, are different from each other in pin-out and/or function,