SN74ALS138N replacement: SN74AS138N or SN74ALS138AN

Hello All,

One of our companies legacy boards has a SN74ALS138N IC on it and I need to update the board. However, in looking for this component the closest available are the SN74AS138N or SN74ALS138AN.

My question is: what is the difference between these two and/or which is the most similar (if not the same) to the original SN74ALS138N?

Thank you for your time.


The part SN74ALS138AN would be the closest option to the original SN74ALS138N.

I was not able to locate a difference between the SN74AS138N and SN74ALS138N

1 Like

@ entechbob


Here is a Texas Instruments document titled Advanced Schottky Family that will help you understand the development of the different products. I can’t refer you to a specific page number because I found relevant information throughout the article–including a comparison table of many products near the end.

Given that there are some electrical differences between SN74ALS and SN74AS, I would try to work with SN74ALS138AN. Those differences might not be critical for your application, but this removes much of the speculation.



Thank you for your time! Between you and Bill_Gust, I think we all agree!



Thank you for such a detailed answer, I will definitely give this a read through, I appreciate your time! Going with the SN74ALS138AN!