FAQ: Logic and Voltage Translation > Logic Technology >> Current FAQ
The High-speed CMOS (HC) logic family was created as a direct replacement for older bipolar junction transistor based transistor-transistor logic (TTL) devices, such as the SN7400 and the SN74LS00. It has been around since 1982 and remains a popular choice for 2.5-V, 3.3-V, and 5-V applications today.
Some of these parts were translated into Japanese and renamed to SN74HCxxA. They have their own datasheets with identical specifications to the non-A versions, and are advertised on the TI Japan website. The primary difference between the "A" and non-"A" devices is that the "A" devices have a datasheet in Japanese, and the non-"A" versions do not. There are other minor differences, namely that the "A" versions have not been updated in a very long time (since 1998) and thus are likely out of date. Some non-"A" versions have been temperature extended to support 125C, and their specifications have been adjusted accordingly.
TI recommends using the SN74HCxx version of parts when presented with the choice. These devices will have the latest datasheets available on TI.com with the most up-to-date specifications, and can directly replace any "A" version..