Abstract: A low power transponder circuit comprises two comparators coupled to a signal input section, wherein only a first comparator is active before a valid wake-up signal is detected and validated. The first comparator preferably consumes less power than the second comparator, and the second comparator preferably operates at a higher speed than the first comparator, such that valid received signal processing is performed on a signal from the second, higher speed comparator. Reference voltage levels for the two comparators can also be modified during circuit operation with either information stored in the transponder or by data received in a valid received signal.