Broadband Sequential Load-Modulated Balanced Amplifier Without Auxiliary Output Matching Network

A novel broadband sequential load-modulated balanced power amplifier (SLMBA) without an auxiliary output matching network is proposed in this letter. In contrast to prior approaches, the proposed SLMBA employs out-phased current combining (OCC) to control impedance, enabling the auxiliary transistors to achieve good matching inherently. Under this configuration, the proposed SLMBA attains a high power utilization factor and low phase dispersion, thereby facilitating easier satisfaction of the phase alignment condition across a wide bandwidth. To better characterize the phase difference, phase characteristics of the output coupler are considered in the theoretical analysis. For demonstration, a 1.55–2.65-GHz SLMBA is designed and prototyped. The experimental results indicate a drain efficiency of 58.4%–66.6% at saturation and 45.6%–60.6% at 10-dB output back-off (OBO) for the proposed SLMBA. Meanwhile, a saturation output power of 42.7–43.7 dBm is also obtained.