1-V rail-to-rail bulk-driven CMOS OTA with enhanced gain and gain-bandwidth product

This paper introduces a CMOS amplifier input stage with extended input common-mode voltage range, suitable for operation in extremely low-voltage environments. The approach is based on a bulk-driven input differential pair, in which the gain and the gain-bandwidth product are enhanced by means of a partial positive feedback loop. The bulk-driven input transistors allow obtaining a very wide input voltage range, while the partial positive feedback leads to an effective transconductance improvement. The proposed input stage has been used to design a 1-V OTA. Post-layout simulated results, obtained in 0.35-μm standard CMOS technology, are given.