A DC-50-GHz Direct-Coupled Self-Biased 50-nm Quasi-E-Mode GaN MMIC Amplifier Based on a 237-GHz f_T-Multiplier

This work is believed to be the first report of a single-supply quasi-enhancement-mode GaN-based monolithic microwave integrated circuit (MMIC) amplifier that operates from dc to 50 GHz. The quasi-E-mode GaN high electron mobility transistors (HEMTs) have an f _T of 120 GHz and a positive turnon voltage, Vgs-on, that enables an all positive-supply, regulated self-bias over threshold variation, and two-stage direct-coupled frequency response down to dc. Core to the quasi-E-mode design topology is a 237-GHz f _T -multiplier transconductance gain stage to enhance the broad bandwidth response. The quasi-E-GaN MMIC obtains a gain of 11.4 dB at dc, 7 dB at 40 GHz, and 5.5 dB at 50 GHz. The 3-dB bandwidth is 31 GHz with return-losses <; -10 dB over the 50-GHz frequency band. The MMIC amplifier is realized in a compact 0.6 × 0.5 mm ² area on a 4-mil SiC substrate. Quasi-E-mode GaN HEMT-based circuit architectures can enable high performance and functionality in a compact size, which has far-reaching implications for scalable broadband millimeter-wave radio applications.