A standard-cell-based CMFB for fully synthesizable OTAs

In this paper, we propose a fully standard‐cell‐based common‐mode feedback (CMFB) loop with an explicit voltage reference to improve the CMRR of pseudo‐differential standard‐cellbased amplifiers and to stabilize the dc output voltage. This latter feature allows robust biasing of operational transconductance amplifiers (OTAs) based on a cascade of such stages. A detailed analysis of the CMFB is reported to both provide insight into circuit behavior and to derive useful design guidelines. The proposed CMFB is then exploited to build a fully standard‐cell OTA suitable for automatic place and route. Simulation results referring to the standard‐cell library of a commercial 130 nm CMOS process illustrated a differential gain of 28.3 dB with a gain‐bandwidth product of 15.4 MHz when driving a 1.5 pF load capacitance. The OTA exhibits good robustness under PVT and mismatch variations and achieves state‐of‐the‐art FOMs also thanks to the limited area footprint.