400 series TLL overview
The 7400 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 7400 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 mid-1960s the 7400 series became the main standard set of logic widely used in electronic digital circuits. There were earlier TTL series of chips. Motorola launched a logic family with the trade name MTTL (Motorola Transistor Transistor Logic), and other series were launched by national Semiconductor, Fairchild and Signetics.
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 7400 series chips could be bought for a few cents each.