Are you confusing a "Wheatstone bridge" with an "H bridge"? I can't understand why anyone would want to reverse polarity as the H bridge does for uses such as reverse motion in servos. An H bridge does not rectify AC signals, although, a Wheatstone bridge does. As far as how a DC pulse is created, whether it from a bridge or mosfet, the end signal is still the same. Only, one is digital(mosfet), and the other is analog(bridge).