The passive diode bridge is a simple circuit to rectify DC voltages. However, the two diodes in the input-to-output path waste power, about 1.4W for every 1A, and dissipate heat. Since power available to a PoE PD is constrained by classification levels, the power wasted in the diode bridges signifies a potential savings waiting to be unlocked for application purposes. The heat dissipated raises the ambient temperature, complicating thermal design and requiring board area to be reserved for heat sinking purposes, raising the PD’s size and cost.