7400 series

As 74xx chips a group of integrated circuits ( ICs) is referred to in digital electronics. The numbers of all circuits (chips) begin with the digits " 74 ", hence the name. These chips contain simple logic gates to complex arithmetic units. Based on components that included only the basic logic functions, more complex circuit functions have been implemented in a component over time.

The series was developed in the 1970s by Texas Instruments and is extended as before. The oldest chips exist virtually unchanged since then. The sequence of digits with four to six digits is counted continuously. The best-known representative is the 7400, a 4-way NAND gate with two inputs each.

Meanwhile, various 74xx logic families have been developed that have been improved over the original, especially in speed and power consumption. They are supported by additional letters (one or up to five letters) between " 74 " and " xx" in example 74LS00 (low power Schottky ). The original series has now lost much of its meaning and is rarely used.

Housing

Most 74xx chips exist as DIL and SMD chips in SMD package forms. They are offered with different prefix letters of many semiconductor manufacturers. Furthermore, logic devices available in a ceramic DIL package.

Operating voltage

The original logic families have been operated with a supply voltage of 5.0V. As a further development of logic families towards ever higher frequencies, a reduction of the operating voltage, for example, 3.3 V or 2.5 V was made ​​in the same context. For the interconnection of logic families with different operating voltages (for example, 3.3 V to 5.0 V), special logic families have been developed which have compatible logic levels at the input and at the output to other logic families.

Logic

The original logic families were produced in the bipolar technology. Over time logic families are then added in CMOS technology and in BiCMOS technology. The logic families for very high clock frequencies are now realized almost exclusively in the CMOS or BiCMOS technology.

Circuit development

In the circuit design today dominate logic families on a low power consumption at the same time a high maximum switching frequency. In practice logic families with 3.3 V or 2.5 V are often used, as other components such as PLDs, FPGAs, ASICs and modern microprocessors are now operated with the lower supply voltages. Furthermore, individual gate functions or individual flip- flops in new developments of modules have virtually no more meaning. As far as possible, this complex logic components are used, include the complete circuit functions in a single component, or programmable logic devices (PLD or FPGA components ) are used. Usually, the logic devices are now used in SMD package. On the part of semiconductor manufacturers were often developed different component series for use in various continuous operating temperature ranges.