An Efficient Class-G Stage for Switching RF Power Amplifier Applications

An efficient class-G stage based on a class-D power amplifier (PA) for switching RF PA applications is described. Class-G operation is achieved by introducing one additional transistor in a cascoded class-D PA, that can reduce area as well as enhance efficiency when compared to prior class-G designs. In addition, a multi-level switching operation is proposed which provides stacked class-G PA operation without using any additional switches. The stacked PA can avoid the requirement for an extra supply voltage for class-G operation. The efficiency and losses in the proposed design, as well as conventional designs, at various output power levels are analyzed by utilizing these in a 5-bit switched-capacitor PA (SCPA). A stacked class-G design with single supply voltage is also compared to an unstacked dual-supply class-G design. While the proposed approach has been explored in an SCPA, the approach can be applied to any switching RF PA architecture that employs a class-D PA.