Exploratory design, development and demonstration of a compact switchmode power amplifier for underwater acoustic transducers is proposed. This amplifier will permit the highly efficient excitation of a high-power broadband sonar projector over a minimum octave frequency band around the mechanical resonance of the transducer. At the selectable tuned frequency such an amplifier/transducer system will produce t high-fidelity acoustic signal. The objectives of the phase I exploratory effort are: (I) to demonstrate feasibility of such a power amplifier, (ii) to determine an optimum design of a~ power amplifier for high-power underwater acoustic transducers, and, finally, (III) to demonstrate the viability of the proposed concepts by building and evaluating a small-scale prototype of the proposed power amplifier. A set of performance specifications reflecting the requirements of the us navy will first be determined. Then, using these specifications, the proposed design and trade-off studies will considered and evaluated several families of a resonant power amplifiers. To demonstrate the viability of the proposed optimum design, a small-scale prototype breadboard will be built and evaluated. Finally, after an optimum amplifier configuration has been determined, a preliminary design of the power amplifier will be presented.