High-Efficiency SiGe-BiCMOS E-Band Power Amplifiers Exploiting Current Clamping in the Common-Base Stage

Abstract

This paper proposes high-efficiency E-band power amplifiers (PAs) in SiGe-BiCMOS based on a common-base out- put stage. A comparison between common-emitter and common- base configurations proves the latter yields higher output power, enhanced linear range, and robustness against self-heating issues. Furthermore, the base–emitter junction of the BJT in common base can be exploited to implement the current-mode version of the well-known diode voltage clamper, so that the dc cur- rent tracks the signal current. This yields an improvement of efficiency, particularly in power back-off. Two PA designs are described: a single-path, two-stage amplifier and a second version delivering higher output power with transformer-based power combining at minimal efficiency degradation. At 80 GHz, the two PAs deliver 18- and 20.5-dBm OP 1d B and 19- and 21.5-dBm Psat. The PAE at OP 1d B is 22% and 20%; at 6-dB back-off, it is still 8.5% and 7.2%, respectively. The prototypes demonstrate two— three times higher PAE compared to previously reported silicon PAs with similar output power at the E-band.