The resonant frequency of the buck-boost power amplifier varies with wide-load variation. When the switching frequency of the amplifier is fixed, detrimental current spikes would occur in boost switches. The efficiency would reduce by few percent with possible gate driver erroneous operation. The buck switches normally operates at hard-switching mode. In the disclosure, more efficient zero-voltage switching (ZVS) mode is obtained with an inductive tank placed between multiple phases of buck switches. The formed buck-boost topology is able to operate at the fixed frequency and without current spikes by implementing an active compensation system. As result, all switches operates at ZVS. Additionally, the buck-boost is able to reduce the current rating of the whole system by around 25 % when compared to the classic cascaded buck-boost topology.