A 280 GHz stacked-FET power amplifier cell using 50 nm metamorphic HEMT technology

This paper demonstrates the first stacked-FET monolithic microwave integrated circuit (MMIC) power amplifier cell operating at 280 GHz. Three different circuits were fabricated using 50 nm gate length metamorphic high electron mobility transistors (mHEMT) in combination with grounded coplanar waveguide (GCPW) lines with 14 µm ground-to-ground spacing. First, cascode and stacked-FET configurations at 240 GHz are compared. The stacked configuration exhibits a more broadband small-signal gain response and a 1.3 dB enhancement of output power compared to the cascode cell. Subsequently, a power amplifier cell for operation at 280 GHz was designed and realized. The stacked-FET configuration is chosen due to its superior performance. The 280 GHz power cell demonstrates more than 8.3 dB of small-signal gain from 267 to 302 GHz (12.3%), with a maximum gain of 9.6 dB at 282 GHz, and an output-referred 2 dB compression point of 3.5 dBm.