A 138.39 FoMS, 2.8 nW, 65dB, digital-based OTA for bio-signal processing applications

This paper presents a novel ultra-low-power, high-gain operational transconductance amplifier (OTA) circuit. The design leverages digital cells with transistors biased in the subthreshold region to achieve significant power savings. To enhance performance, a new local common-mode feedback (LCMFB) scheme and an innovative topology are introduced, enabling superior multistage gain without compromising the gain-bandwidth product (GBW) or requiring complex compensation techniques. The proposed OTA achieves a DC gain of 65 dB with a remarkable power consumption of just 2.8nW at a supply voltage of 0.3V. Furthermore, it can operate at supply voltages up to 0.6V, offering greater flexibility and reusability across different applications. The compact layout area of 400 μ m2and its strong figure-of-merit (FOM) demonstrate competitive performance compared to state-of-theart designs. With its exceptionally low power profile, this OTA is ideal for integration into system-on-chip solutions for biomedical signal processing applications powered by energy harvesting techniques.