A study on a diode-bridge type differential capacitance detection circuit

Differential capacitance sensor with movable electrodes is usually applied for accelerometers, pressure gauges, etc. because of its high sensitivity and resolution. Two axis inclination sensor with differential capacitance structure using MEMS (Micro Electro Mechanical Systems) technology has recently been designed for industrial and environmental purposes. The initial capacitance of the sensor should be very low, as few pF, therefore, a C-V converter circuit, which is able to detect very small capacitance variations is required. In this study, the particular principle of a "diode-bridge type differential capacitance detection circuit" has been analyzed. After the mathematical simulations performed by using PSpice simulator, the detection of the capacitance variations in fF order resolution are considered.