A 3.5-GHz SiGe 0.35μm HBT Doherty power amplifier (DPA) on ceramics integrated passive device (CIPD) using flip-chip assembled package for system in package (SiP) integration is reported in this paper. The unit cell power amplifier in the DPA demonstrates a saturated output power of 28dBm and 35% PAE at P SAT. When the complete DPA is operated in the quasi-balanced mode, it demonstrates a P SAT of 30.5dBm (PAE = 31%), and a PAE of 8% at OP 1dB. When the complete DPA is operated in the quasi-Doherty mode, it has a P SAT of 30dBm with the same PAE, and an improved PAE of 27% at OP 1dB. The excellent performance is mainly due to the high Q passive elements of CIPD. To the author's knowledge, this is the first demonstration of a watt-level PA using flip-chip assembled on CIPD process with good performance.