0.4-V Bulk-Driven Operational Amplifier with Improved Input Stage

A new solution for an ultra-low-voltage, low-power, bulk-driven operational amplifier is presented in the paper. The amplifier is based on a new input stage, exploiting the concept of partial positive feedback. As compared with prior work, the proposed input stage offers improvement of all basic performance metrics, including such important parameters as input-referred noise and offset voltage. In order to improve the DC voltage gain of the overall op-amp, a novel solution for an ultra-low-voltage, high-input-resistance common-mode amplifier has also been proposed. Simulated performance of the overall operational amplifier for a 50 nm CMOS process and supply voltage of 0.4 V shows power dissipation of 24 μ W, the open-loop voltage gain of 60dB, and the gain-bandwidth product of 2.18 MHz for 20 pF load capacitance.