Zero crossing detector

A zero crossing detector circuit based on a simplified version of:

Fig. 16-25: Bipolar zero-crossing detector.

in:

Designing Analog Chips by Hans Camenzind.

http://www.designinganalogchips.com/_count/designinganalogchips.pdf

You can read more about this remarkable man who is perhaps best remembered as the designer of the 555 timer:

http://en.wikipedia.org/wiki/Hans_R._Camenzind

http://www.edn.com/electronics-blogs/anablog/4394211/Hans-Camenzind-remembered