High power density, high efficiency 1 W SiGe power HBT for 2.4 GHz power amplifier applications

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 (P_sat) 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 (PAE_max) of up to 75% was obtained, with a power gain of 11.4 dB at a P_3-dB of 29.0 dBm. In addition, the real part of the source impedance (R_in) was measured to be as high as 28 Ω. The impedance transfer ratio, R_in/R_System 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.