Transimpedance bandwidth performance of an HBT loss-compensated coplanar waveguide distributed amplifier

The authors report the results of a coplanar waveguide loss-compensated GaAs HBT distributed amplifier which achieves 48 dB Ω (25 Ω) with an upper bandwidth response of 19.3 GHz while consuming only 75 mW of DC power. The corresponding gain is 8.2 dB with a 19.5 GHz upper frequency band edge. When biased for maximum gain-bandwidth product, the amplifier dissipates 117 mW of DC power and achieves 14.5 dB gain with a 16.5 GHz bandwidth, and a corresponding transimpedance of 55 dB Ω (562 Ω) with a 14.4 GHz bandwidth. The resulting transimpedance-bandwidth product is 8.1 THz Ω which is about a factor of 2 greater than previously reported conventional HBT-based direct-coupled topologies when normalised to HBT device cut-off frequency f_T. These results suggest that the HBT-based distributed amplifier approach has performance advantages for high data rate (⩾20 Gbit/s) optical communication systems