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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).
Some TTL logic parts were made with an extended military-specification temperature range. These parts are prefixed with 54 instead of 74 in the part number. [1] A short-lived 64 prefix on Texas Instruments parts indicated an industrial temperature range; this prefix had been dropped from the TI literature by 1973.
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.
Transistor–transistor logic uses bipolar transistors to form its integrated circuits. [12] TTL has changed significantly over the years, with newer versions replacing the older types. Since the transistors of a standard TTL gate are saturated switches, minority carrier storage time in each junction limits the switching speed of the device.
7400 series parts were constructed using bipolar junction transistors (BJT), 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 ( BiCMOS ).
A multiple-emitter transistor is a specialized bipolar transistor mostly used at the inputs of integrated circuit TTL NAND logic gates. Input signals are applied to the emitters . The voltage presented to the following stage is pulled low if any one or more of the base–emitter junctions is forward biased, allowing logical operations to be ...
The 74181 is a 4-bit slice arithmetic logic unit (ALU), implemented as a 7400 series TTL integrated circuit. Introduced by Texas Instruments in February 1970, [1] it was the first complete ALU on a single chip. [2] It was used as the arithmetic/logic core in the CPUs of many historically significant minicomputers and other devices.
Symbol Effective internal circuit composed of Schottky diode and bipolar junction transistor. Standard transistor–transistor logic (TTL) uses transistors as saturated switches. A saturated transistor is turned on hard, which means that it has a lot more base drive than it needs for the collector current it is drawing.