| Summary: | 碩士 === 國立清華大學 === 電子工程研究所 === 100 === In recent years, with the progress of CMOS-MEMS tech-nology, MEMS microphone gradually replaced the traditional Electret Condenser Microphone(ECM)and became the mainstream in consumer electronic products such as various mobile devices and hearing aids. When the sensor and the readout circuit are integrated together as a system-on-a-chip (SoC), because the capacitive variation of MEMS microphone is in the range of femto-Farad, a low-noise signal-translation in the readout circuit is very important.
In order to meet the requirements for low-noise, low-cost applications in the sound frequency (low frequency) range, this work uses a junction field effect transistor (JFET), which is integrated in the 0.35um CMOS standard process, as the input device for the readout circuit so as to reduce the input referred low-frequency noise. In addition, a MOSFET is in comparison with the JFET to verify the feasibility. The readout circuit includes a low-noise amplifier and a high dynamic range sigma-delta modulator (SDM) to process the signal. The simulated results of the SDM show that the peak SNDR and the dynamic range are 70.4dB and 102.9dB, respectively. The peak SNDR of the readout circuit is 69.8dB. The chip size is 556um x 381um.
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