A 0.5-V 0.02% THD Bulk-Driven OTA for Continuous-Time Applications in 180 nm CMOS

This paper introduces a 0.5-V, two-stage, pseudo-differential bulk-driven operational transconductance amplifier with high gain and linearity for low-power continuous-time applications. The input stage’s common-mode feedback utilizes a linear resistor detector with a conductance reduction cross-coupled pair to mitigate the loading effect of the common-mode detector resistor at ultra-low power operations. Temperature dependence of the conductance reduction circuit is compensated. The impact of the conductance reduction circuit on linearity performance is explored. The output stage employs a class-AB topology and utilizes a phase lead compensator to stabilize the OTA. Implemented in 180 nm CMOS technology, this OTA achieves a DC gain and slew rate of 68 dB and 26.1 V/ $\mu $ s, respectively, under a capacitive load of 10 pF. The total power consumption is $34.2~\mu $ W. With unit gain feedback configuration, the measured total harmonic distortion is only 0.02% at an output amplitude of 500 mVpp. Test results validate the proposed circuit, positioning it competitively compared to state-of-the-art designs.