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We present a micro-chip implementation of a low current measurement system for biomedical applications using capacitive feedback that exhibits 190 fA of RMS noise in a 1 kHz bandwidth. The sampling rate is selectable up to 100 kHz. When measuring the amplifier noise with a 10 G Ω resistor and a 47 pF capacitor at the input, typical of cell membrane capacitance in DNA and patch clamp experiments, the measured RMS noise was 2.44 pA on a 50 pA signal in a 10 kHz bandwidth. Two channels were implemented on 630 × 440 μm2 using a 0.5- μm 3-metal 2-poly CMOS process. Each channel consumes 1.5 mW of power from a 3.3 V supply. We measured the characteristics of an artificial lipid bilayer similar to the ones used in DNA sequencing experiments via nanopores.
Biomedical Circuits and Systems, IEEE Transactions on (Volume:6 , Issue: 2 )
Date of Publication: April 2012