A 125$μ$W 8kS/s Sub-pA Area-Efficient Current Sensing 45nm CMOS ADC for Biosensing
This paper presents a 125$μ$W, area efficient (0.042mm2) 81dB DR, 8kS/s current sensing ADC in 45nm CMOS capable of sensing sub-pA currents. Our approach combines the transimpedance amplifier (TIA) and ADC into a unified structure by folding a low-noise capacitive TIA into the first stage integrator of a 2nd order Delta-Sigma modulator. The dominant DAC feedback noise is mitigated by utilizing current scaling via slope modification by an integrator and differentiator pair.
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