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

2002, IEEE Transactions on Microwave Theory and Techniques

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,