A Capacitive sensor readout circuit with low power mode and variable gain operations

This paper proposes readout circuits capable of sensing capacitance variations at the output of a capacitive sensor in the range of 0.5pF to 1.5pF using the concept of switched capacitance. Capacitive circuits are the most preferred for low power VLSI applications. We make use of a supply voltage of 1V as we intend to develop a low power module. This module will use the concept of programmable biasing which is useful for reducing the amount of power dissipation. It also includes programmable gain option to select the required gain based on the capacitance variation range. All results and simulations were done using the GPDK's 90nm and 180nm CMOS process technology library.