Design of fully integrated RF power amplifiers using voltage combining method

Abstract

The design of a fully-integrated power amplifier with a reasonable output power, efficiency and gain has been one of the major challenges in today’s pursuit of a single-chip solution to RF transceivers. This work presents the design of RFIC power amplifiers using voltage combining method. The voltage combining method using transmission line transformer is particularly useful in silicon. It allows individual transistors to drive more current with lower voltage swings, since the power combining function is merged with impedance transformation. Based on this concept, a 1.9GHz differential power amplifier for polar transmitter applications is implemented using 0.18μm CMOS technology. A differential Class-E topology is employed to achieve high efficiency by exploring its soft-switching property. All the matching components are fully integrated with 50Ω input and output matching. The power amplifier delivers 1W at the supply voltage of 2.5V, with a power added efficiency of 30%. This technique is also applied to HBT power amplifier design to achieve a compact and high-efficiency design. A single-chip 5GHz linear power amplifier is designed using GaAs HBT process. It exhibits a 27dBm output 1dB compression point with 32% maximum power-added efficiency at 5.3GHz.