A Bi-Directional Near-Ground Current Sensor With Reconfigurable Unidirectional Gains

A bi-directional near-ground-output low-side-input current-sensing amplifier (CSA) is fabricated in 65-nm CMOS. Two negative-feedback paths drive dual pMOS transistors to conduct an auto-switching bi-directional current detection with configurable unidirectional gains, which reduces the conventional switching-point distortions and doubles the sensing accuracy. A DC shifter based on a negative-feedback loop, avoids an input large current to benefit the sensing linearity, and optimizes the common-mode rejection ratio (CMRR). Various noise and offset suppression mechanisms are also utilized. Experimental results show that the proposed CSA achieves an offset voltage of 1.58 µV,a noise level of 37.5 nV/√Hz, and a CMRR up to 159 dB, with the power dissipation of 0.36 mW from a 1-V supply and an active area of 0.19 mm². Reconfigurable or different unidirectional gains and near-ground input / output voltages are achieved, which are different from the existing designs.