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LM393: Question about rail-to rail

Part Number: LM393

Hello team,

I have a question about rail to rail description from product folder.

In my understanding, both devices need 2V headroom at the input side, but does not at the output side. I'd like to make sure what these pictures represent because there is no further information at the datasheet.

Can you please let me know Rail-to-rail is Out means? Is there difference between non-B version and B version in terms of output side?

Best Regards,


  • Hello Austin,

    Correct. The input is NOT R-R input, and requires the 2V headroom.

    Both are open-collector outputs, so technically they can be R-R out if the pull-up is to the comparator supply voltage. So "No" or "Out" are technically valid.

    If the device is R-R input, it would say "In".

    The LM393B is a direct, drop-in, improved replacement for the LM393 and will behave the same or better.