Power amplifiers are critical components for audio, grid simulator and Power Hardware-in-the-Loop (PHIL) applications with the requirement of low cost, high bandwidth and fast dynamics. This thesis proposed an innovative combination of a GaN-based inverter and boundary control implemented in an FPGA to realize a high-bandwidth switching power amplifier with high bandwidth-switching frequency ratios. The control strategy, implementation considerations and the experimental results are presented in this thesis. The influences of the non-ideal factors, including the limited bandwidth of the components and the limited resolution of the analog-to-digital converter when implementing boundary control in a system, have been discussed and analyzed. A proposed compensation method to mitigate the negative impact on the performance of the boundary control from the overall delay has been verified experimentally. This thesis has proposed an analytical method to estimate system bandwidth with boundary control based on the frequency response of the RLC circuit and the specification of the system. Experiment results have verified the proposed method. The Power Amplifier achieves a 30 kHz average switching frequency with the bandwidth of 7.1 kHz, the rated power of 1000 W, amplifier gain of 100 V/V and the power efficiency of 97.78%. The experimental results show that the system can track the step changes of the reference and the load in tens of microseconds.