Evaluation of highly sensitive C/V converter with an inverter for CMOS/MEMS integration

In this paper, fabrication and evaluation results of a small-scale, in-pixel type C-V converter with chopper stabilized CMOS inverter is presented for MEMS capacitive sensor array. MEMS pixel structures can be fabricated by post-CMOS process, and integrated with the small-scale integrated CMOS C-V converters. Since this C-V converter can be configured by only a CMOS inverter and switches, power consumption and circuit area are very small as compared to C-V converters with operational amplifier. Also, since this circuit has amplifier function, sensitivity of C-V conversion can be very much improved as compared to passive type C-V converters. Reduction of stray capacitance is important for precise detection of capacitance, and it is also realized by this simple circuit configuration. A prototype C-V converter was fabricated and evaluated successfully. Its high performance of capacitive detection realized by the active C-V conversion has been demonstrated in the experimental results.