Design of High-Gain Sub-THz Regenerative Amplifiers Based on Double-Gmax Gain Boosting Technique

This article reports the concept of a double maximum achievable gain (double- G_{\mathrm{ max}} ) core for the implementation of sub-terahertz high-gain amplifier design. The double- G_{\mathrm{ max}} core is a G_{\mathrm{ max}} core that adopts another linear, lossless, and reciprocal network that satisfies the G_{\mathrm{ max}} condition onto an even number of cascaded transistor-level G_{\mathrm{ max}} cores. It is shown that the double- G_{\mathrm{ max}} core, due to its regenerative nature, can achieve much higher gain per stage than that of the same number of cascaded G_{\mathrm{ max}} cores while satisfying the unconditional stability. Implemented in a 65-nm CMOS process, by adopting the proposed double- G_{\mathrm{ max}} core, 247- and 272-GHz two-stage amplifiers achieve the peak gain of 18 and 15 dB, the gain per stage of 9 and 7.5 dB, and the PAE of 4.44% and 2.37%, respectively, while dissipating 21.5 mW.