Science Fair Project Encyclopedia
Early 7400 series parts were constructed using bipolar transistors, although most newer sub-series use CMOS technology or a combination of the two (BiCMOS). Originally the bipolar circuits provided higher speed but consumed more power than the 4000 series of CMOS devices. Bipolar devices are also limited to a fixed power supply voltage, typically 5V, while CMOS parts often support a range of supply voltages.
Milspec rated devices for use in extreme conditions are available as the 5400 series. A shortlived 6400 series was rated for an intermediate (industrial) temperature range.
The 7400 family contains many hundreds of devices that provide everything from basic logic gates to special purpose bus transceivers and Arithmetic Logic Units (ALU). Specific 7400 functions are described in a list of 7400 series integrated circuits.
- 7400 series subfamilies
- BCT - BiCMOS, TTL compatible input thresholds, used for buffers
- ABT - Advanced BiCMOS, TTL compatible input thresholds, faster than ACT and BCT
- C - CMOS 4-15V operation similar to 4000 series
- HC - High speed CMOS, similar performance to LS
- AC - Advanced CMOS, performance generally between S and F
- AHC - Advanced High-Speed CMOS, three times as fast as HC
- FC - Fast CMOS, performance similar to F
- LCX - CMOS with 3V supply and 5V tolerant inputs
- LVQ - Low voltage - 3.3V
- LVX - Low voltage - 3.3V with 5V tolerant inputs
- VHC - Very High Speed CMOS - 'S' performance in CMOS technology and power
Many parts in the HC, AC, and FC families are also offered in "T" versions (HCT, ACT, and FCT) which have TTL-compatible input thresholds. The non-T parts require CMOS input thresholds.
The 74L family is a relatively low-power, but slower version of the 74 family.
The 74H family is the same basic design as the 7400 family with resistor values reduced. This reduced the typical propagation delay from 9ns to 6ns but increased the power consumption. The 74H family provided a number of unique devices for CPU designs in the 1970s.
The 74S family, using Schottky circuity, 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 than the original 74 family; it became the most popular variant once it was widely available.
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 found in newer microprocessor and personal computer CPU devices.
Although the 7400 series was the first defacto industry standard TTL logic family, there were earlier TTL logic families such as the Sylvania SUHL family, Motorola MC4000 MTTL family (not to be confused with RCA CD4000 CMOS), the National Semiconductor DM8000 family, and the Signetics 8200 family.
The 7400 NAND gate was the first product in the series.
The 5400 and 7400 series were used in many popular minicomputers in the Seventies and early Eighties. 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.
Hobbyists and students equipped with wire wrap tools, a 'breadboard' and a 5-volt power supply could also experiment with digital logic referring to how-to articles in Byte Magazine and Popular Electronics which featured circuit examples in nearly every issue.
As of 2005, individual chips can be purchased for approximately $0.25 each, depending on the particular chip. Purchased in bulk the price per unit falls to a few pennies per package.
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