One or more circuit arrangements for a biosensor are provided. A circuit arrangement includes an ion sensitive sensor, a differentiator electrically connected to the ion sensitive sensor, an AC signal level comparator electrically connected to the differentiator and a decision circuit electrically connected to the AC signal level comparator. In some embodiments, the AC signal level comparator includes at least one of a first comparator or a second comparator. A method of detecting a bio-reaction is also provided.