Low-Voltage Bulk-Driven Operational Amplifier With Improved Transconductance

This paper presents two low-voltage bulk-driven amplifier input stages with enhanced transconductance. The idea is to introduce auxiliary differential pairs into a conventional bulk-driven stage to boost its transconductance. A low-voltage cascode biasing circuitry based on EKV models is also employed to ensure proper operation of the proposed input stages. An operational amplifier is then implemented with the proposed input stages and biasing circuits as its core building blocks and including a modified low-voltage class AB output amplifier to guarantee rail-to-rail output voltage range. The overall amplifier was implemented in a 0.35 μm n-well CMOS process using 1-V power supply. The measurement results show significant improvement in the performance of the operational amplifier compared to prior arts.