Distributed active transformer-a new power-combining and impedance-transformation technique (original) (raw)

In this paper, we compare the performance of the newly introduced distributed active transformer (DAT) structure to that of conventional on-chip impedance-transformations methods. Their fundamental power-efficiency limitations in the design of high-power fully integrated amplifiers in standard silicon process technologies are analyzed. The DAT is demonstrated to be an efficient impedance-transformation and power-combining method, which combines several low-voltage push-pull amplifiers in series by magnetic coupling. To demonstrate the validity of the new concept, a 2.4-GHz 1.9-W 2-V fully integrated power-amplifier achieving a power-added efficiency of 41% with 50-input and output matching has been fabricated using 0.35m CMOS transistors. Index Terms-Circular geometry, CMOS analog integrated circuit, distributed active transformer, double differential, harmoniccontrol, impedance transformation, low voltage, power amplifier, power combining. I. INTRODUCTION A MONG THE several building blocks necessary to construct today's holy grail in wireless communication, the "single-chip radio," power amplifiers have been one of the most significant challenges. Several results have been published in this field, but none have reported a watt-level fully integrated power amplifier using silicon technology. Until now, the highest output powers achieved by fully integrated power amplifiers in standard silicon processes are 85 mW [1] delivered to a differential 50-load with a power-added efficiency (PAE) of 30% and 100 mW with a drain efficiency of 16% [2], both implemented in CMOS technology. Other works using CMOS [3], [4] or Si bipolar [5], [6] processes rely on the use of external passive components such as bond wire inductors,