Difference Between 74HCxx and 74LSxx digital logic integrated circuit

Submitted by Jaya on Tue, 09/04/2018 - 12:19
If you see that the pinouts of 74HCxx and 74LSxx looks similar, but in some projects hobbyist mention that, use 74HCxx not 74LSxx for particular schematics.
So my question is that what are the practical differences in these two digital logic integrated circuits. Can we replace HC with LS in any circuit? 
And if there are differences, than which one is better for what type of projetcs?

Hi Jaya welcome to CircuitDigest Forums,

Blindly speaking the 74HCXX is the modern day replacement for the old  74LSXX ICs. Since the 74HCXX uses MOSFET technology it can operate in a wide range of voltage at higher frequencies compared to the 74LSXX series that works on transistor technology.

So the reason that some circuits particularly need 74HCXX is that they might have a different operating voltage other than +5V or might have to work with higher frequencies. For instance in a 3.3V system you cannot use a 74LCxx you have to use a 74HCxx

Hope this helps !!!

  Joined August 16, 2016      997
Tuesday at 12:29 AM

Thanks for answering aswith now I understand the difference.

But the problem is that my local vendor only supplies 74LSxx IC's, so can I use them on my 5V circuits?


  Joined September 04, 2018      1
Tuesday at 11:58 AM

Most probably yes, but I am not very sure because I do not know where you are trying to use them.

I remember using these 74LSxx gates extensively during my school days since my lab  did not have an alternative. Just maintain a regulated supply voltage of 5V and they should work fine. If you are dealing with fast switching (higher frequencies) then moving to a 74HCxx series should be considered.

  Joined August 16, 2016      997
Tuesday at 12:29 AM