7400 Logic Series Technologies Summary

Understand the differences between the different families of technologies used within the different types of 7400 series logic families: 74xx, 74LS, 74LV, etc

Logic IC families & Technologies Includes:
IC logic families & technolgies summary chart Numbering schemes 7400 Series TTL 7400 sub-families listing

The 7400 series of logic chips has been particularly successful since it was first launched in 1966.

Although the original chips are now dated, they can still be used, but the main way in which these chips have left their legacy is that new sub-families or technologes have been developed which meet the needs of today's logic chip requirements.

There are sub-families or technologies that support the low voltage requirements of many of today's designs, as well as providing fast operating times, etc.

To give a good idea of what the different sub-families or technologies provide, I've assembled some tables providing the basic information.

Bipolar Series of 7400 Logic
Family	Name	Supply (V)	t_pd (ns)	I_OL(mA)	I_OH (mA)	Details
74	Standard TTL	5 ± 5%	22	16	-0.4	Original TTL introduced in 1966.
74H	High speed	5 ± 5%	10	20	-0.5	Higher speed, but higher dissipation compared to standard TTL.
74L	Low power	5 ± 5%	60	3.6	-0.2	Lower power, lower performance.
74S	Schottky	5 ± 5%	5	20	-1	Used Schottky diode to reduce delays.
74LS	Low power Schottky	5 ± 5%	15	8	-0.4	Same technology as 74S but with lower power and slightly slower performance.
74F	Fast	5 ± 5%	3.9	20	-1	This was originally the Fairchild version of the 74AS family.
74AS	Advanced Schottky	5 ± 10%	4.5	20	-2
74ALS	Advanced Schottky	5 ± 10%	4.5	20	-2

The Bipolar series of the 7400 logic chips started off this popular and standard series, but as technology advanced and lower power requirements came to the fore, CMOS technology was utilised for new sub-families within the overal series.

BCMOS & BiCMOS Series of 7400 Logic
Family	Name	Supply (V)	t_pd (ns)	I_OL(mA)	I_OH (mA)	Details
74C	CMOS	3.0 - 15	60	0.36	-0.36	Similar to the buffered 4000 series and levels not compatible with standard TTL.
74HC	High speed CMOS	2.0 - 6.0	15	4	-4	Performance similar to 74LS and with CMOS logic levels.
74HCT	High speed CMOS	5 ± 10%	15	8	-4	Similar performance to 74LS and with TTL logic levels.
74AHC	Advanced high speed CMOS	2.0 - 5.5	5.5	8	-8	Up to three times as fast as 74HCT and utilises TTL logic levels.
74AC	Advanced CMOS	2.0 - 6.0	8	24	-24	CMOS logic levels.
74ACT	Advanced CMOS	5.0 ± 10%	8	24	-24	TTL logic levels.

As the operating voltages for microprocessor have fallen to reduce power consumption and increase the levels of integration, so too the operating voltages for some new sub-families have followed suit.

In order to be able to interface with them and run from the same supplies, new sub-families have been created.

Low Voltage CMOS Series of 7400 Logic
Family	Name	Supply (V)	t_pd (ns)	I_OL(mA)	I_OH (mA)	Details
74LVT	Low voltage BiCMOS	2.7 - 3.6	4.1	32	-20	TTL logic levels with 5V tolerant inputs and outputs.
74LV	Low voltage CMOS	2.7 - 3.6	18	6	-6	TTL logic levels.
74LVC	Low voltage CMOS	2.0 - 3.6	6	24	-24	TTL logic levels.
74ALVC	Advanced low voltage CMOS	1.65 - 3.6	3	24	-24	3.3V tolerant inputs and output.s
74LVX	Low voltage high-speedCMOS	2.0 - 3.6	9.7	4	-4	TTL logic levels, 5V tolerant inputs, and faster than other types at low voltages.
74AUC	Advanced ultra-low voltage CMOS	0.8 - 2.7	2	9	-9	Very low voltage logic chips with 3.3V tolerant inputs.

These represent some of the more widely used 74 series logic sub-families. The basic concept has been continued since the first chips were released in the mid 1960s, and although it is rare to see PCBs full of these chips, they are still used as logic surrounding microprocessors, microcontrollers and the like.