High performance SiGe HBT power unit-cell for S-Band open collector adaptive bias power amplifier design

Abstract

A SiGe heterojunction bipolar transistor (HBT) power unit-cell for S-Band high efficiency linear power amplifier with an open collector adaptive bias linearizer was designed and fabricated in this paper. The unit-cell was investigated in both electrical and thermal performances and 34 unit-cells were then combined as a power device for output stage. An adaptive linearizer for the output stage was constructed with an open collector HBT bias circuit and improved the power gain (Gp), output 1dB compressed power (OP1dB), power added efficiency (PAE), and output third-order intermodulation point (OIP3) when compared to those of traditional adaptive bias circuit. The measured power amplifier achieved a Gp of 13dB, an OP1dB of 22dBm with a PAE of 28.6%, and an OIP3 of 31.4dBm. Compared to traditional adaptive bias technique, the proposed linear power amplifier improved the output power of 2dB, PAE (at P1dB) of 8.6% and OIP3 of 3.4dB. The fabricated die size, including pads, is less than 1.44mm2.