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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).
Often two level shifters are used, one at each system: A line driver converts from internal logic levels to standard interface line levels; a line receiver converts from interface levels to internal voltage levels. For example, TTL levels are different from those of CMOS. Generally, a TTL output does not rise high enough to be reliably ...
TTL logic levels are different from those of CMOS – generally a TTL output does not rise high enough to be reliably recognized as a logic 1 by a CMOS input. This problem was solved by the invention of the 74HCT family of devices that uses CMOS technology but TTL input logic levels.
Higher speed than the original 74 series, at the expense of power dissipation. TTL logic levels. [24]: 6–2 [25]: 3–6 74L Low-Power 5 V ±5% 60 ns 3.6 mA −0.2 mA 1967 [26]: 72 Same technology as the original 74 family, but with larger resistors to lower power consumption at the expense of gate speed. TTL logic levels. Now obsolete.
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.
The logic level on one wire is always the complement of the other. The principle is similar to that of low-voltage differential signaling (LVDS), but with different voltage levels. Differential TTL is used in preference to single-ended TTL for long-distance signaling. [4]
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.
MAX232 chip in DIP-16 package The die of a MAX232 MAX232 pinout: Red: power, Yellow: charge pump capacitors, Blue: outputs, Green: inputs, Pins 9–12: TTL/CMOS I/O voltages. The MAX232 is an integrated circuit by Maxim Integrated Products, now a subsidiary of Analog Devices, that converts signals from a TIA-232 (RS-232) serial port to signals suitable for use in TTL-compatible digital logic ...