Abstract
This paper investigates the operating principle, energy efficiency, and frequency-dependent characteristics of a current-mode class-D power amplifier (CMCD) intended for 5G FR1 (sub-6 GHz, below 6 GHz) applications, specifically within the 3.4-3.8 GHz band. The amplifier is based on a classical push-pull CMCD architecture operating in switching mode and demonstrates the potential for high theoretical efficiency by reducing switching losses through minimizing the temporal overlap between current and voltage waveforms. The analysis examines the peak drain voltage, current and voltage waveforms, load conditions, and frequency-dependent parameters. Simulation results show stable operation across 3.4-3.8 GHz, while indicating a decreasing trend in gain and efficiency as frequency increases. This behavior is attributed to increased transistor switching losses and the impact of parasitic parameters of passive components. The results confirm that the CMCD power amplifier is suitable for 5G FR1 mobile communication systems, particularly around 3.5 GHz, and that practical accuracy can be further improved by employing realistic RF transistor models (LDMOS/GaN/CMOS) and explicitly accounting for parasitic effects