A novel heterojunction bipolar transistor active feedback design

This paper reports on the results of a novel active feedback amplifier design using heterojunction bipolar transistors. The design incorporates positive feedback to increase the gain bandwidth response by as much as 50 %. The active feedback amplifier achieves a gain of 13.8 dB and a 3-dB bandwidth of 15.6 GHz. The active feedback is economical in size in comparison to a spiral inductor implementation. In addition, the active feedback network includes a means for electronically tuning the active feedback circuit in order to adjust the bandwidth response. A two-stage design achieves a tuneable bandwidth from 4-10 GHz with a fixed gain of 20 dB. The tuneability that this design offers is a convenient means for recovering from gain and bandwidth degradation due to process variation and fixture parasitics.>