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The first CMOS family of logic integrated circuits was introduced by RCA as CD4000 COS/MOS, the 4000 series, in 1968. Initially CMOS logic was slower than LS-TTL. However, because the logic thresholds of CMOS were proportional to the power supply voltage, CMOS devices were well-adapted to battery-operated systems with simple power supplies.
Transistor–transistor logic (TTL) is a logic family built from bipolar junction transistors.Its name signifies that transistors perform both the logic function (the first "transistor") and the amplifying function (the second "transistor"), as opposed to earlier resistor–transistor logic (RTL) and diode–transistor logic (DTL).
His patent also showed how the Schottky transistor could be used in DTL circuits and improve the switching speed of saturated logic designs, such as the Schottky-TTL, at a low cost. In 1971, Texas Instruments introduced the 74S TTL logic family with Schottky diodes. Later, it was included in the 74LS, 74AS, 74ALS, 74F TTL logic families too.
A few alphabetic characters to designate a specific logic subfamily may immediately follow the 74 or 54 in the part number, e.g., 74LS74 for low-power Schottky. Some CMOS parts such as 74HCT74 for high-speed CMOS with TTL-compatible input thresholds are functionally similar to the TTL part. Not all functions are available in all families.
An integrated circuit made in CMOS is not a TTL chip, since it uses field-effect transistors (FETs) and not bipolar junction transistors (BJT), but similar part numbers are retained to identify similar logic functions and electrical (power and I/O voltage) compatibility in the different subfamilies.
Current mode logic (CML), or source-coupled logic (SCL), is a digital design style used both for logic gates and for board-level digital signaling of digital data. The basic principle of CML is that current from a constant current generator is steered between two alternate paths depending on whether a logic zero or logic one is being represented.
This schematic diagram shows the arrangement of four OR gates within a standard 4071 CMOS integrated circuit. OR gates are basic logic gates, and are available in TTL and CMOS ICs logic families. The standard 4000 series CMOS IC is the 4071, which includes four independent two-input OR gates. The TTL device is the 7432.
The 4000 series was introduced as the CD4000 COS/MOS series in 1968 by RCA [1] as a lower power and more versatile alternative to the 7400 series of transistor-transistor logic (TTL) chips. The logic functions were implemented with the newly introduced Complementary Metal–Oxide–Semiconductor (CMOS) technology.