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A large?scale antenna system (LSAS) with digital beamforming is expected to significantly increase energy efficiency (EE) and spectral efficiency (SE) in a wireless communication system. However, there are many challenging issues related to calibration, en?ergy consumption, and cost in implementing a digital beamforming structure in an LSAS. In a practical LSAS deployment, hybrid digital?analog beamforming structures with active antennas can be used. In this paper, we investigate the optimal antenna configu?ration in an N × M beamforming structure, where N is the number of transceivers, M is the number of active antennas per trans?ceiver, where analog beamforming is introduced for individual transceivers and digital beamforming is introduced across all N transceivers. We analyze the green point, which is the point of maximum EE on the EE?SE curve, and show that the log?scale EE scales linearly with SE along a slope of ?lg2/N. We investigate the effect of M on EE for a given SE value in the case of fixed NM and independent N and M. In both cases, there is a unique optimal M that results in optimal EE. In the case of independent N and M, there is no optimal (N, M) combination for optimizing EE. The results of numerical simulations are provided, and these re?sults support our analysis.