Design of a broadband current mode class-D power amplifier with harmonic suppression

摘要

Current mode class-D power amplifiers (CMCD-PA) are attractive for fully integrated PA implementation as the output capacitance of the active device can be absorbed in the output matching network that can be realized with minimum number of components. This paper presents a simplified design approach for CMCD PA design using an integrated balun transformers. Expressions are derived for the optimum device sizing for second harmonic suppression resulting in improved efficiency. An expression of amplifier efficiency as a function of device size is is presented proving that current mode class-D amplifier yields higher higher efficiency than a class-E amplifier for the same device size. The amplifier is implemented in 130 nm CMOS process and encapsulated in QFN package. Measurement results show that the amplifier exhibits broadband response between 1.4 and 2.1 GHz with peak output power of 26.8 dBm at 1.8 GHz using a 2.4 V supply. PAE remains above 40 % for the entire range while peak PAE is 48 %. Results show a good match between simulation and measurement work. Voltage sweep of the amplifier shows that it can be used in supply modulation based LINC techniques.