A High-Performance, Low-Noise Class-AB Folded-Cascode Op-Amp with Novel Biasing Circuit for Biomedical Applications

This study introduces a high-performance folded cascode (FC) operational amplifier (Op-Amp) architecture with a novel biasing circuit and area-optimized custom layout for enhanced performance. The proposed architecture has a gain of 120 dB and can go up to 127.3 dB of DC gain. The Op-Amp can deliver a Common Mode Rejection Ratio (CMRR) of more than 130 dB, and a Power Supply Rejection Ratio (PSRR) of up to 110.93 dB, and only occupies an area of 0.03133 mm². The design exhibits a gain-bandwidth product of 5.6 MHz, a phase margin of 81.84 degrees, and a slew rate of up to 4.61 V/µs, surpassing comparable designs found in existing literature. A novel biasing circuit improves the management of the PSRR while minimizing the influence of channel length modulation effects. The architecture utilizes a class-AB output stage to improve the driving strength of the Op-Amp. Additionally, it incorporates a PMOS-driven FC input stage, which effectively mitigates flicker noise, and satisfies the demanding criteria of biomedical applications.