Abstract-This letter has demonstrated the state-of-the-art SiGe power heterojunction bipolar transistors (HBTs) operating at 8 GHz. In a common-base configuration, a continuous wave output power of 27.72 dBm with a concurrent power gain of 12.19 dB was measured at a peak power-added efficiency of 60.6% from a single SiGe HBT with a 3-µm emitter finger stripe width and a 1340 µm 2 total emitter area. The highest power-performance figure of merit (FOM) of 3.8 × 10 5 mW · GHz 2 achieved from the device was resulted from using an optimized SiGe heterostructure and a compact device layout, which is made possible with a heavily doped base region.Index Terms-Common-base (CB), heterojunction bipolar transistors (HBTs), SiGe, X -band.
Linearity characteristics between common-emitter (CE) and common-base (CB) SiGe HBTs are compared at different frequencies using a new analytical expression of third-order intermodulation distortion (IMD3) versus input power (P in ) for the first time. Verified with simulations and measurements, the study shows that there is a potential trade-off between CE and CB configurations for linear power amplification on power gain and linearity in the low-and medium-frequency ranges. In the high-frequency range, CB configuration shows both higher power gain and better linearity than the CE configurations.
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