A novel HBT distributed amplifier design topology based on attenuation compensation techniques

We report on a novel HBT distributed amplifier design which achieves the highest gain-bandwidth product (GBP) per device f_T so far reported for HBT distributed amplifiers. This paper introduces a new design topology for HBT DA´s which incorporates attenuation compensation on both the input and output transmission lines. A four-section HBT DA using this novel topology achieves a gain of 15 dB and a 3-dB bandwidth of >15 GHz. The resulting gain-bandwidth product is 84 GHz. When normalized to the device f_T , this DA achieves the highest normalized gain-bandwidth-product figure of merit for HBT DA´s, ≈3.67, which is a 55% improvement over existing state-of-the-art performance. Attenuation compensation of the input transmission line is realized using HBT active impedance transformations. The resulting transistor configuration consists of a common-collector driving a common-emitter-cascode transistor pair. This configuration offers 15-20 dB more available gain for the device unit cell, and results in gain-bandwidth product improvements of 200% over a conventional common-emitter DA configuration. This paper discusses the design theory, techniques, and measurements of this newly developed HBT distributed amplifier topology