A D-Band Differential Amplifier With Cross-Couple of Series-Connected Capacitor and Transmission Line-Based Dual-Frequency G_max-Core

This brief presents a novel wideband and high-gain amplifier that utilizes a differential dual-frequency G_max-core with a cross-coupled network incorporating a capacitor and a transmission line (TL). The proposed cross-coupled network connects a capacitor to the TL and cross-couples the connected capacitor and TL, providing opportunities for design optimization. Through adjustable capacitance insertion, the proposed network achieves significantly higher equivalent reactance with a shorter TL length compared to a conventional TL-only embedding network. Consequently, this innovative structure enables the implementation of a G_max -core requiring high reactance in a compact size, a feat unattainable with a conventional TL-only network. To validate the effectiveness of the proposed dual-frequency G_max-core, a 3-stage D-band differential amplifier is designed using a 40 nm CMOS process. The measurement results demonstrate a peak gain of 14.2 dB at 149.9 GHz, a 3-dB bandwidth of 28.2 GHz, and an OP1dB of 1.9 dBm at the center frequency of 144.5 GHz, with a DC power dissipation of 65.8 mW.