Abstract: A switching power amplifier for use in low-frequency sonar applications. s amplifier comprises a set of four switching transistors arranged in a bridge configuration for switching a power source through a highly resonant, low-frequency, underwater transducer. The signal to be amplified is taken from a signal generator, filtered, converted to voltage logic levels, delayed and modified a predetermined amount in time to prevent a power short circuit through the bridge due to slow transistor switching, and applied to a set of four voltage transformers. A different voltage transformer is coupled to each of the switching transistors in the bridge circuit. These voltage transformers are coupled to switch their respective bridge transistors only when their primary currents are collapsing, thus effectively decoupling the bridge transistors and the power source from the signal conditioner and driver delay circuitry.