Broadband High-Efficiency Quasi-Class-J Power Amplifier Based on Nonlinear Output Capacitance Effect

In this brief, a broadband high-efficiency quasi-Class-J power amplifier (PA) based on nonlinear output capacitance effect is proposed. With the influence of the voltage across between drain and source ( <tex-math notation="LaTeX">vDS </tex-math> ) at the over-driven condition, the negative second harmonic termination has been generated by the nonlinear output capacitance ( <tex-math notation="LaTeX">Cₒᵤₜ </tex-math> ). Since the proposed PA is driven into saturation, the current magnitude can be increased which improves the output power and efficiency. Meanwhile, the fundamental termination is modulated near the real axis of the Smith chart by the second harmonic termination, which reduces the <tex-math notation="LaTeX">Q </tex-math> -factor to extend the bandwidth. It is possible to achieve the saturated PA working in the wide frequency band. Finally, the proposed PA shows a relatively high performance of greater than 39.6 dBm saturated output power, and delivers an average of 64 % drain efficiency (DE) from 3.5 to 5.5 GHz.