Model of a MEMS sensor using a common gate MOSFET differential amplifier

The design, modelling and feasibility of a MEMS sensor based on a common gate metal-oxide-semiconductor field effect transistors (MOSFET) differential amplifier is presented. A pair of adjacent MOSFETs shares a common gate electrode that is suspended in a torsional configuration over the transistor gate regions. Rotation of the common gate alters the relative spacing between the gate tips and the substrate changing the gate capacitance of each transistor. Connection of the transistor pair in a differential readout configuration generates a differential current flow through the MOSFET pair. This sensor integrates transduction and amplification as movement of the MEMS gate modulates the relative gate capacitance and drain current of each transistor. The differential configuration provides a high common mode rejection ratio and the estimated sensitivity is 68 muA (fF(-1)) and the responsivity of the sensor is 2.2 mV/degree.