High accuracy current sense amplifier with extended input common mode range

A high accuracy current sense amplifier with input common mode range extending beyond the positive supply rail is presented. The offset voltage is minimized using an auto-zero topology with a fully differential internal path. Characteristics of the presented amplifier include an input voltage range of 30V, independent of the supply rail, a fixed gain with a typical gain error of 0.05% and a referred-to-input offset voltage of less than 10μV in the -40°C to 125°C temperature range. The proposed architecture was implemented in a 0.5μm CMOS process and its performances were confirmed by post-layout simulation results.