Loop Oscillation Analysis of MEMS Resonant Pressure Sensor Readout Circuit

This paper presents a CMOS automatic gain control (AGC) readout circuit for Micro Electro-Mechanical System (MEMS) resonant pressure sensor. The oscillation conditions for MEMS loop and the accompanying parasitic loops are analyzed in this paper. The parasitic capacitance between the driving and sensing electrodes of the sensor will lead to the electrical oscillation and prevent electrical-mechanical oscillation. The conditions of loop gain that need to be met to solve the above negative effects are discussed. A low noise Trans-Impedance Amplifier (TIA) is proposed to improve system noise performance. Fully differential structure is adopted in the circuit to reduce common-mode interference. The circuit achieves an equivalent input current noise of 0.41 pA/√Hz@100kHz, consumed 4.3mA current under a 5-V supply voltage.