D-Band Common-Base Amplifiers with Gain Boosting and Interstage Self-Matching in 0.18- μm SiGe HBT Technology

This paper presents two D-band amplifiers fabricated in a 0.18- μm SiGe heterojunction bipolar transistor process. A single-ended amplifier employs a five-stage common-base topology, and a differential amplifier combines two of the single-ended chains. To overcome the limited available gain of the given technology at D-band, a gain-boosting technique based on positive feedback is adopted for each gain cell. In addition, the input and output impedances of the gain cell are conjugate-matched by adjusting the positive feedback; thus, no external components are needed for interstage matching. This improves the gain and bandwidth while minimizing the chip size. The single-ended amplifier exhibits a measured gain of 7.5 dB at 123 GHz with a 3-dB bandwidth of 25 GHz. The differential amplifier shows a measured gain of 20.3 dB at 115 GHz with a 3-dB bandwidth of 13 GHz. The output power values of the two amplifiers are 2.6 and 6.7 dBm, respectively. The chip sizes are small at 0.22 and 0.40 mm², respectively.