Research Of Fully Differential Amplifier Of Micromechanical Gyroscope

Silicon micromechanical gyroscope is a new type of inertial sensor, in both civil and military areas, it is studied widely and deeply for its broad foreground of evolution and application. The fundamental principle of vibration micromechanical gyroscope is analysed first. Grounded on the initial ASIC of micro gyroscope of MEMS center, single ended sense circuit is improved to differential sense circuit. And the important block trans-resistrance amplifier of self-excitated drive circuit is designed.Single ended sense circuit has some disadvantages that are poor common-mode noise rejection and poor sensing capacity for small capacitance. So this paper presents a differential sense circuit which is used to capacitive frame gyro. This circuit can improve the performance of the total circuits and the system. As the former stage, the noise of the integrator has a bad influence on resolution. A folded-cascode fully differential op amp is used for integrator with"fast sensing"common- mode feedback circuit. Differential sense circuit rejects common-mode noise and provides a larger sensing sensitivity. R-MOSFET-C two order fully differential lowpass is used in 1st stage of sense circuit. Compared to active-RC filter with linear resistors, it's request for processing is not very rigorous, while have higher linearity. The IC is simulated. Frequency response of R-MOSFET-C filter tally with active-RC filter. -3dB frequency of the filter is 13.5kHz, attenuation of frequency response is achieved -41.01dB at the frequency of carrier wave.Trans-resistrance amplifier in drive circuit is used for current to voltage conversion, while provides appropriate gain for amplify drive signal. Trans-resistrance amplifier uses a folded-cascode fully differential op amp with a variable resistor in feedback. The variable resistor is implemented using a MOS switch and a MOS device operating in the linear region. Depending on the control voltage at MOS switch, trans-resistrance amplifier implements adjustable gain.The IC is simulated by Hspice. When the input angle velocity is 1°/s, sensitivity of the output of single ended sense circuit is 7.25 mV/°/s. The sensitivity of differential sense circuit is 15.82mV/°/s.