ITWissen.info - Tech know how online

transistor transistor logic (IC) (TTL)

TTL Logic, Transistor Transistor Logic (TTL), is a basic circuit for logic circuits, implemented as an integrated circuit( IC). Transistor Transistor Logic states that it is a logic operation based on transistors and multi-emitter transistors, diodes and resistors. The diodes are used for voltage dissipation, the resistors are used as working resistors and for voltage division.

Such a TTL logic can be a multi-emitter transistor working as an AND gate. A NOT gate connected downstream inverts the AND gate into a NAND gate.

The logic levels of TTL circuits are between 0 V and +5 V. The logic "0" must have a voltage of up to 0.8 V at the input and one of up to 0.4 V at the output. The logic "1" is represented at the input with voltages of over 2.0 V and at the output with voltages of over 2.4 V. Levels in between are undefined and can result in a "0" or a "1".

a) Multi-emitter transistor as OR gate, b) TTL logic as NOT gate

a) Multi-emitter transistor as OR gate, b) TTL logic as NOT gate

The higher voltage input potential takes into account possible tolerance deviations in the output voltage, so that outputs connected to the input are still detected correctly even if the levels are slightly exceeded.

Switching levels of TTL logics

Switching levels of TTL logics

The power dissipation for TTL logics is more than 10 mW per gate. With the LVTTL technology (Low Voltage TTL) the supply voltage has been reduced to 3.0 V to 3.6 V and thus the power dissipation. In addition to the well-known TTL logics, there are also various TTL subfamilies that are characterized by lower power consumption, such as the Low Power TTL( L-TTL), or by short switching times, such as the High Speed TT L ( H-TTL) and the Fast TTL (F-TTL). Furthermore, the Schottky-TTL( S-TTL), the Low-Power Schottky-TTL( LS-TTL), the Advanced Schottky( AS) and the Advanced-Low-Power Schottky-TTL( ALS-TTL).

Informations:
Englisch: transistor transistor logic (IC) - TTL
Updated at: 10.02.2012
#Words: 295
Links: through the lens (photo camera) (TTL), logic, integrated circuit (IC), identification code (IC), operation
Translations: DE
Sharing:    

All rights reserved DATACOM Buchverlag GmbH © 2022