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This paper presents a low-power precision instrumentation amplifier intended for use in wireless sensor nodes. It employs a capacitively-coupled chopper topology to achieve a rail-to-rail input common-mode range as well as high power efficiency. A positive feedback loop is employed to boost its input impedance, while a ripple reduction loop suppresses the chopping ripple. To facilitate bio-potential sensing, an optional DC servo loop may be employed to suppress electrode offset. The IA achieves 1 V offset, 0. 16% gain inaccuracy, 134 dB CMRR, 120 dB PSRR and a noise efficiency factor of 3. 3. The instrumentation amplifier was implemented in a 65 nm CMOS technology. It occupies only 0. 1 mm^2 chip area (0. 2 mm^2 with the DC servo loop) and consumes 1. 8 A current (2. 1 A with the DC servo loop) from a 1 V supply.
Fan et al. (Tue,) studied this question.