A 1.9 nW, Sub-1 V, 542 pA/V Linear Bulk-Driven OTA with 154 dB CMRR for Bio-Sensing Applications

In this paper, a new technique for improvement on the DC voltage gain, while keeping the high-linearity in symmetrical operational transconductance amplifier (OTA) bulk-driven (BD) topology is proposed. These features are achieved by allying two topological solutions: enhanced forward-body-biasing self-cascode current mirror, and source degeneration. The proposed concept is demonstrated through simulations with typical process parameters and Monte Carlo analysis on nominal transistors of the CMOS TSMC 180 nm node. Results indicate that the proposed OTA can achieve a very small transconductance, only 542 pA/V while keeping a voltage gain higher than 60 dB, 150 dB CMRR, and high linearity of 475 mVpp (1% THD), consuming only 1.9 nW for a supply voltage of 0.6 V. This set of features allows the proposed OTA to be an attractive solution for implementing OTA-C filters for the analog front-ends in wearable devices and bio-sensing.