In this paper, an improved layout and thermal management of eight unit-cells SiGe power HBT with emitter area of 8 × 0.6 × 10 μm2 were designed for high power density and efficiency performance. The on-wafer power characteristics were measured using an ATN load-pull system under class-AB operation at 2.4 GHz. The power HBT achieved a 1-dB compression power (P-1 dB) of 27.3 dBm and a saturation output power (Psat) of 30 dBm which was correspond to a power density of 2.6 mW/μm2 for the emitter area. A high peak power added efficiency (PAEmax) of up to 75% was obtained, with a power gain of 11.4 dB at a P3-dB of 29.0 dBm. In addition, the real part of the source impedance (Rin) was measured to be as high as 28 Ω. The impedance transfer ratio, Rin/RSystem is only 0.56 which relaxes the need for a high quality passive component (inductor) for on-chip input matching. This advantage makes it easier for the HBT to be integrated with other silicon-based transceiver in an RF System-on-Chip (SoC) design.