Transistor–transistor logic facts for kids

A two-input TTL gate, a basic building block

Transistor–Transistor Logic (TTL) is a special kind of digital electronic circuit. It uses tiny electronic switches called transistors and resistors to make decisions. It's called "transistor–transistor logic" because transistors do all the important work. They handle the logic (like saying "yes" or "no") and also make the signals stronger.

Many integrated circuits, which are like tiny electronic brains on a chip, use TTL technology. You can find TTL circuits in lots of places. They are used in computers, industrial control systems, and even musical synthesizers.

TTL circuits understand two main states: "0" and "1". These represent "off" and "on" or "false" and "true." A voltage below 0.5V (very low) is seen as a "0." A voltage between 4V and 5V (higher) is seen as a "1." This simple system allows computers to process information.

Different Types of TTL Circuits

Just like there are different types of cars, there are different types of TTL circuits. These types, or "families," were developed over time to be faster, use less power, or work better in certain situations.

Bipolar TTL Families

These are some of the older types of TTL circuits. They use a kind of transistor called "bipolar junction transistors."

• 74 series: This was the original "standard" TTL family. It's very old now and not used much anymore.
• 74L (Low Power): These used less power than the original 74 series but were also much slower.
• 74LS (Low Power Schottky): This was a very popular type. It was faster than 74L and used less power than the original 74 series. Many older computers and electronics used these.
• 74ALS (Advanced Low Power Schottky): An improved version of LS, offering even better speed and lower power use.
• 74F (Fast): These were designed to be very quick, faster than many other types.

CMOS TTL Families

These families use a different type of transistor called "CMOS" (Complementary Metal-Oxide-Semiconductor). CMOS circuits generally use less power than bipolar ones.

• 74HC (High-speed CMOS): These are fast, similar to the 74LS series, but use much less power. They are very common today.
• 74HCT (High-speed, TTL Compatible): These are like 74HC but are designed to work easily with older bipolar TTL circuits.
• 74AC (Advanced CMOS): These are even faster CMOS circuits.
• 74LVC (Low Voltage CMOS): These circuits work with lower voltages, which helps save power and makes them suitable for modern portable devices.

BiCMOS TTL Families

BiCMOS circuits combine both Bipolar and CMOS technologies. This allows them to get the best features from both, like high speed from bipolar and low power from CMOS.

• 74ABT (Advanced BiCMOS): These are fast and powerful, often used for sending signals between different parts of a circuit.

Images for kids

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  A real-time clock built from TTL chips around 1979. It shows how these chips were used to build useful devices.

See also

In Spanish: Tecnología TTL para niños