Embodiments provide tripping unit of a circuit breaker. The tripping unit includes a magnet, a bimetal member extending alongside of the magnet, and an armature pivotable on the magnet, wherein the armature having an engagement portion engageable with the bimetal member at a moveable end of the bimetal member. Circuit breakers including triggering mechanisms and tripping units are also disclosed, as are low-profile, electronic circuit breakers including a maximum transverse width (Wt) limited to occupy only a single standard breaker panelboard location. System and methods are provided, as are other aspects.