Broadband dielectric spectroscopy CMOS readout circuit for molecular sensing

The readout circuit of broadband dielectric spectroscopy (BDS) for molecular sensing is described. The circuit performs a high-precision capacitance-to-current conversion and amplification of the difference of signals generated by two very small capacitors in the conventional CMOS 0.18 /spl mu/m technology. We make use of the continuous-time common mode error amplification and offset-cancelling low-noise lock-in architecture to measure the admittance as a function of frequency. The power consumption of the front-end is under 30 /spl mu/W/channel. It has a quasi-linear conversion ratio of 164 pA/aF.