The design and implementation of a high efficiency Class-J mode RF power amplifier (PA) for wireless communications applications is described here. In this study, a broadband class-J power amplifier with GaN HEMT transistor is designed to achieve 40 dBm output power and 10 dB gain, high efficiency and linearity performance in the 2.5-3.5 GHz frequency band. Experimental results indicate good agreement with simulations verifying and demonstrating the class-J mode operation. The obtained power added efficiency (PAE) is above 68% and the output power is 39.84 dBm at an input drive of 30 dBm. High efficiency is achieved in the frequency range from 2.5 GHz to 3.5 GHz. Simulation and experimental results show that the class-J RF power amplifier can be realized more effectively in terms of a better compromise between power and efficiency trade-offs over a significant RF bandwidth than conventional class-AB/B operations. the ACPR value for the linearity measurement was found to be around -30 dBc.