Design and Comparison of Two SiGe Complementary Millimeter-Wave Power Amplifiers

This paper focuses on two complementary stacked bipolar power amplifiers (PAs): two-transistor stack and four-transistor stack. Based on the advanced 130-nm SiGe BiCMOS process, a comprehensive comparison is carried out regarding complementary mechanism, circuit topology, key performance parameters and parasitic effects. Through systematic formula derivation and analysis, their performance boundaries and design trade-offs are revealed. The measurement results show that the two-transistor stack achieves superior power-added-efficiency (PAE) of 25% with 20.5-dB gain and 17-dBm saturated output power at 24 GHz. Higher output power of 20 dBm and more competitive gain of 25 dB are obtained by the four-transistor stacked PA with 21.7% PAE. Both of the two designs exhibit excellent overall performance, demonstrating an optimal balance among gain, efficiency, and output power. Furthermore, a compact area of approximately 0.08 mm² is achieved by eliminating the need for power-combining and choke inductors. It is promising for area-constrained high-performance bipolar millimeter-wave power amplifier designs.