Logic IC Families

- details and chart or table of the different logic IC families including RTL, DTL, TTL, ECL to 7400 series and the modern low power low voltage versions, etc.

Since the first idea of logic circuits were developed, there have been very many families of circuits.

After the introduction of the integrated circuit, IC, logic blocks were naturally contained within chips. Accordingly a variety of logic IC families spawned, each offering different capabilities and facilities.

Over the years, the most widely used overall family has been the 7400 series ICs. Initially launched as straight 7400 series integrated circuits, this logic IC family has spawned many variants which has enabled it to remain in use until this day.

Logic families chart / table

A tabulation of the major logic families with relevant data is given below. Links to further pages with more in depth information for each logic family are given within the table.

Logic Family or Series Technology Supply voltage
Basic Details Link
RTL Resistor Transistor Logic ~3 This form of logic used resistors and transistors. It was first introduced around 1962.
DTL Diode transistor logic 5 This logic family or series used diodes on the inputs to create functions such as AND and OR and then had transistors on the output.
MECL I Emitter coupled logic -5.2 This was the first type of logic IC family to be developed and it appeared around 1962.
ECL III Emitter coupled logic -5.2
(-5.19 - -5.21)
This was an improved form of ECL. It was very fast having toggle speeds of up to 500 MHz, but it was very current hungry and chips would run very warm. However its speed meant that it remained in use, often being used in RF applications such as frequency synthesizers where very fast counters were needed. Running from a negative supply it was difficult to interface to many other elements of the design.
ECL 10k Emitter coupled logic -5.2
(-5.19 - -5.21)
An updated version of ECL, although it had a top toggle speed of around 125 MHz
ECL 100K Emitter couple logic -5.2
(-5.19 - -5.21)
An even later version of ECL but with a maximum clock speed of 350 MHz.
7400 TTL 5
(4.75 - 5.25)
Introduced around 1964, this series of logic used transistors in all areas of the chip. It became an industry standard. 7400 logic family
74L00 TTL (Low Power) 5
(4.75 - 5.25)
Introduced in 1964, the low power 7400 series of logic devices used lower power than the standard TTL family, but at the expense of speed and output capability.
74H00 TTL (High speed) 5
(4.75 - 5.25)
Again introduced in 1964, this high speed TTL offered a speed of almost twice that of the standard 7400 logic family, but at the expense of increased current consumption.
74S00 TTL (Schottky) 5
(4.75 - 5.25)
Using Schottky diode technology, this form of TTL was able to offer operating speeds of around four times that of the standard 7400 logic family
74LS00 TTL (Low power Schottky) 5
(4.75 - 5.25)
The low power Schottky logic family offered lower propagation delays, higher toggle speeds and lower power levels per gate than the original 7400 logic family. As such it became very widely used for many years 74LS00 logic family
74ALS TTL (Advanced low power Schottky) 5
(4.5 - 5.5)
Advanced low power Schottky giving increased speed and lower power when compared to low power Schottky.
74F00 TTL (Fast) 5
(4.75 - 5.25)
Fast TTL, offering speeds that are four times that of standard 7400 series TTL. While the speed is essentially the same as Schottky TTL, it provides the speed at around a quarter of the power.

Over the years very many families of logic ICs have been developed and many remain in use today. ECL is rarely used, and obviously the older forms of 7400 TTL logic are not as widely used. 74S00 and other formats have been obsolete for some years.

By Ian Poole

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Logic families IC numbering 7400 series 74LS00 series

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