EXTENDING THE BANDWIDTH PERFORMANCE OF HETEROJUNCTION BIPOLAR TRANSISTOR-BASED DISTRIBUTED-AMPLIFIERS

An InAlAs/InGaAs-InP HBT CPW distributed amplifier (DA) with a 2-30 GH z l-dB bandwidth has been demonstrated which benchmarks the widest ban dwidth reported for an HBT DA. The DA combines a 100 GHz fmax and 60 G Hz ft HBT technology with a cascode coplanar waveguide DA topology to achieve this record bandwidth. The cascode gain cell offers 5-7 dB mor e available gain (MAG) than a common-emitter, and is used to extend th e amplifier's upper frequency performance. A coplanar waveguide design environment is used to simplify the modeling and fabrication, as well as to reduce the size of the amplifier. Novel active load termination s for extending the DA's lower frequency response were separately demo nstrated. The active loads are capable of extending the lower bandwidt h performance by two decades resulting in performance below 45 MHz. Th is work explores both design techniques and technology capability whic h can be applied to other distributively matched HBT circuits such as active baluns for mixers, active combiners/dividers, and low de power- broadband amplifiers.