Would you mind giving me a hint of what or where to look to understand how to shift the input as you mention below?

Kind regards,
Lindy

> 
> After properly amplifying the input signal, run it through a Schmitt
> trigger (comparator). For such a simple circuit you don't have to use a
> bipolar supply, so you probably won't. Which means that you may amplify
> your input signal and shift it so that 0 input is at, say, 2.5V. Then you
> put your comparator threshold at 2.5V.


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