Coupled Feedback Differential Amplifier as a High-Power Terahertz Amplifier

This work proposes an amplifier architecture called coupled feedback differential amplifier (CFDA) that can reduce the effective gate-drain parasitic capacitance (Cgd) of a transistor. The effective parasitic capacitance reduction offered by the proposed CFDA allows the adoption of large size transistor to improve the saturated output power (Psat) performance of a THz amplifier. In addition, an adoption of Gmax concept into the proposed CFDA boosts its power gain performance. Therefore, the proposed CFDA has good performance in terms of both Psat and power gain as confirmed by the simulation results. The simulated Psat of the proposed CFDA shows around 6 dB improvement compared to that of the conventional single-ended high-gain THz amplifier, while still having similar level of power gain performance.