Series power combining: Enabling techniques for Si/SiGe millimeter-wave power amplifiers

We review series power combining techniques for power amplifiers that have significantly enhanced the output power and power density of millimeter-wave power amplifiers implemented in Silicon (Si) and Silicon-Germanium (SiGe) integrated circuit processes. Two of the record highpower demonstrations for Si/SiGe have included transistor stacking and sub-quarter-wavelength power combiners. A 30-GHz power amplifier implemented in 45-nm CMOS SOI demonstrates 24.5 dBm of output power with 30% PAE using four stacked FETs. A two-stage, 114-130 GHz power amplifier with stacked HBTs and sub-quarter-wavelength baluns also demonstrates a record 22 dBm output power and 254 mW/mm² output power per unit area.