A follow up question to my last post. Which lettering system is universal to older IC's. Example. If I buy a 75HCXXX can I swap that into a 74LCXXX or 74??XXX. Are the HC the latest and completely backward compatible? If not is there one that is somewhat universal so that if I have a 74LSXXX go out, I can buy a HC or ?? that will work in it' place? I hope my question makes sense.
Thanks Russ
There isn't any other 74 subfamily that is a universal replacement for the others. That's why the still make so many different ones.
The 74HC parts usually cannot substitute for 74LS parts due to the high Vih input threshold. 74HCT is more likely to work as a substitute for
74LS, but there is no guarantee as the timing is not the same.Generally if you have a failed 74LS part, the replacement should be 74LS.
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