As apart of a circuit I am looking to make a comparator based zero crossing detector. I have a question about the correct input condition to the comparator which does not seem to be covered in my www searching.

The non inverting input has a sine wave signal with amplitude +5V to -5v. Can I use a rail to rail comparator (+5V to 0V) and would this require a diode to block most of the negative side of the signal? There are some rail to rail comparators which will go 0.7v below the negative supply.

While I can use a -5V supply rail I'd like to understand what can be used.

Thanks
A

 

This will be the clipping circuit.
If you want to get a smaller voltage less than 0.6V then you can using schottky diode.

 

Take a look at this one.

 

You can do that with an LM393, but please put a 10k or higher resistor in series with the sinewave input so that nothing gets stressed when the signal swings below ground. Also, the LM393 requires a pullup resistor on its output.