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

This paper presents two complementary stacked bipolar power amplifiers (PAs): a two-transistor stack and a four-transistor stack, implemented in a 130 nm SiGe BiCMOS process. A comprehensive comparison is conducted regarding their complementary operation, circuit topologies, key performance metrics, and parasitic effects. Through systematic analysis and derivations, their performance limits and design trade-offs are clarified. Measurement results show that the two-stack PA achieves a power-added efficiency (PAE) of 25%, a gain of 21 dB, and a saturated output power of 18 dBm. The four-stack PA provides a higher output power of 21 dBm and a gain of 26 dB, with a PAE of 21.7%. Both designs demonstrate an excellent balance among gain, efficiency, and output power. By eliminating the need for power-combining and choke inductors, a compact area of approximately 0.08 mm² is achieved. This work highlights the potential of the complementary stacked topology for high-performance bipolar millimeter-wave PA design.