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~\mu $ V, a noise level of 37.5 nV/ $\surd $ 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.