TTL Turns 50
Here is an article that made my heart glow:
Fifty years of TTL
Transistor-transistor logic (TTL) is the same age that I am. I have
fond memories of designing, building, and debugging TTL projects when I
was a teenager. I even designed and built a home security system using
TTL as recently as 2002.
The TTL Data Book (1976)
I still have on my bookshelf the Texas Instruments "TTL Data Book"
pictured above. It sits next to Signetics' "Integrated Circuits" and
Intel's "Component Data Catalog" from the same timeframe (1974 and 1978,
You are probably wondering in an age of billion-transistor chips, how
much use is there for chips containing tens or hundreds of transistors?
TTL is still manufactured and used today as "glue logic" - connecting
billion-transistor chips may still require TTL decoders and
transceivers. A trivial task like ANDing together two signals is best
done by a 74LS08 TTL chip. The main obstacles to using TTL are
relatively high voltage (5 volts, although 3.3 volt families are
available) and glacial (5-15ns) propagation delays.
The 74LS08 Quad 2-Input AND Gate
The longevity of TTL is a result of its "building block" approach. TTL
chips do not do much by themselves - a typical TTL chip might contain
four 2-input NAND gates, a 4-bit counter, a 3-8 decoder, four 2-1
multiplexers, an 8-bit shift register, or an 8-bit transceiver. The
power comes from putting together tens or hundreds of TTL chips to
create complex systems. TTL is like Tinkertoys - a bucket of parts that
one can assemble into anything one imagines. Modularity and
interoperability go a long way.