An Energy-Efficient Three-Stage Amplifier Achieving a High Unity-Gain Bandwidth for Large Capacitive Loads without Using a Compensation Zero

This letter presents a high-gain energy-efficient three-stage amplifier, which employs buffering-based pole relocation and dual-path structure. The proposed design does not rely on the introduction of compensation zero and preserves the unity-gain bandwidth (GBW) of the local feedback loop (LFL). Compared to the topologies using active-zero insertion, the 3rd pole is formed with a much smaller capacitance (parasitic capacitance), enabling it to be placed at a significantly higher frequency while consuming lower power. Moreover, the parasitic pole at the main path is bypassed by using an auxiliary path. Thus, the 3rd pole can be pushed to a higher frequency more easily than the topologies using an active zero. As a result, the GBW of the LFL in the proposed work is less limited. The proposed design improves the state-of-the-art FOML by 36%, LC-FOMS by 26%, and LC-FOML by 218%, while preserving robustness of the performance.