A kind of capacitive sensor chip which using three-order Sigma-Delta modulation technique to realize direct conversion of capacitance to digital signal is introduced. It extends measurable capacitance range by compensation capacitor matrix

and take advantage of current-starved OTA to improve operational amplifier（ OPAMP） current efficiency

as well as reduce the overall power consumption. This capacitance sensor is realized in SMIC 0. 18 μm CMOS technology and Cadence tool is used for simulation validation of circuit. Measurement results show that the modulation performs three-order noise shaping function in transfer time of 0. 8 ms

while consuming 18. 6 μA under 2 V supply voltage. The measurable input capacitance range is 0 ～ 8 p F

and good linearity is achieved.