Novel distributed baseband amplifying techniques for 40-Gbit/s optical communication

GaAs MESFET baseband amplifiers using novel distributed amplification schemes have been developed. The key feature of their design is a direct coupling architecture employing two new distributed DC transformers. One is a distributed level-shift circuit and the other is a distributed SCFL level transformer. A two-stage distributed amplifier IC cascaded with the distributed level-shift circuit has a gain of 17 dB with a DC-to-30-GHz bandwidth. This is the best performance so far among all reported GaAs MESFET baseband amplifier ICs. A distributed baseband amplifier IC with the distributed SCFL level transformer can be directly coupled with a GaAs SCFL circuit. This IC also has a DC-to-30-GHz bandwidth with a gain of 7 dB. This is the first IC with an SCFL interface to have such broadband characteristics.