A Fully Differential Rail-to-Rail Capacitance Measurement Circuit for Integrated Cell Sensing

The paper describes a fully differential CMOS circuit for integrated capacitance sensing of living cells. The proposed circuit is based on the charge based capacitance measurement (CBCM) technique which maps differential input capacitances linearly to rail-to-rail differential output voltages. The paper also proposes a shielded current routing bus architecture which will enable the measurement circuit to be incorporated into sensor arrays. The circuit has been designed in a commercially available 1-poly, 8-metal, 130-nm CMOS technology and has been simulated for different input capacitance ranges on the fF scale, appropriate for sensing cell layers or individual cells cultured on-chip. The simulated static response curves and computed calibration curves have been used to evaluate sensitivity and linearity performance metrics of the sensor circuit. The fully differential capacitance measurement approach increases sensor dynamic range and improves output noise resolution thereby providing better discrimination of cell-related phenomena.