A 325 GHz InP HBT Differential-Mode Amplifier

An MMIC amplifier operating at the highest reported frequency up to date for indium-phosphide double-heterojunction bipolar (DHBT) transistor technology is presented. The amplifier chain consists of seven unit-cell stages that contain differential-pair common-base HBTs and compact inverted microstrip matching networks. Amplifier operation in differential mode generates a virtual RF ground at a convenient location inside the unit cell. The measurements at 325 GHz show a small signal gain of 25 dB and a maximum output power of
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1.5 dBm. An amplifier gain of greater than 20 dB is observed over 60 GHz bandwidth extending from 285 to 345 GHz.