A Power-Efficient Adaptively-Biased Class-AB OTA with Improved Gain, Slew Rate, and Reduced Systematic Mismatch

This paper presents a high-performance powerefficient class-AB Operational Transconductance Amplifier (OTA) for biomedical applications. It features a DC gain of 80 dB, a unity-gain bandwidth of 214 kHz and a slew rate of 2 ~V / μ S driving 10 pF as load capacitor. High slew rate value is achieved by using an adaptive biasing, while drawing only 1.47 μ ~A from a 1.8 V power supply. The proposed OTA is stable in unity-gain frequency with 63° phase margin, respected to the load capacitor. The design employs modified cascode current mirrors to achieve higher DC gain and reduce systematic mismatch. The proposed OTA is designed and post-layout simulated in a 0.18 μ ~m CMOS technology. It achieved an input referred noise density of 57 nV / √ Hz, a flicker noise corner frequency of 4 6 5 ~ H z, a common-mode rejection ratio of 8 1 ~ d B, a power supply rejection ratio of 94 dB and a total harmonic distortion of -59 dB. With adaptive biasing and a modified cascode current mirror, the proposed OTA reduced random offset voltage by 5 0 % and power consumption by 2 3 % in comparison with the conventional adaptive-biased structure.