A 0.3-V, nW-power Bulk-Driven Rail-to-Rail 4-Stage OTA in a 180 nm CMOS technology

The paper introduces a four-stage operational transconductance amplifier (OTA) targeting ultra-low-power and ultra-low-voltage applications. The proposed circuit comprises a simple while effective compensation topology which entails a single Miller capacitor and an RC parallel block at the output of the third stage. Implemented in a standard CMOS 180-nm technology and powered at 0.3 V, this work uniquely benefits of power consumption reduction of a factor 39X-33,333X and a rail-to-rail dynamic range when compared with previous 4-stage OTAs. In addition, the proposed solution improves the state-of-the-art of high-gain multi-stage bulk-driven OTAs exhibiting a larger DC gain (>17.9 dB), a 1.9X improved gain-bandwidth product under higher maximum capacitive load (2.85X) and, hence, an increase of the F OM<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</inf> of more than 4.4X.