A fully integrated multi-channel impedance extraction circuit for biosensor arrays

Impedance spectroscopy (IS) is a powerful tool for characterizing materials that exhibit a frequency dependent behavior to an applied electric field. This paper introduces a fully integrated multi-channel impedance extraction circuit that can both generate AC stimulus signals over a broad frequency range and also measure and digitize the real and imaginary components of the impedance response. The circuit was fabricated in 0.5μm CMOS and consumes 355μW at 3.3V. Tailored for protein and lipid bilayer characterization, the signal generator produces sinusoidal waves from 1Hz to 10kHz. To suit a variety of applications, the impedance extraction circuit provides a programmable current measurement range from 100pA to 100nA with a measured resolution of ~100fA. Occupying only 0.045mm² per measurement channel, the circuit is compact enough to include nearly 100 channels and the signal generator on 3 × 3mm die.