| Summary: | 碩士 === 國立高雄應用科技大學 === 電子工程系碩士班 === 103 === The main purpose of this work is to design a fully differential chopper stabilized analog front-end sensing circuit for microphone. By cascading an eighth order Butterworth low-pass filter, the whole circuit forms a complete readout circuit design. By using the modulation technique, this design can effectively reduce resolution error caused by the low frequency noise and input offset voltage of operational amplifier. So the signal noise ratio (SNR) is therefore increased.
In our design, the fully differential operational amplifier contains two amplification stages and a pair of complementary common-mode feedback amplifier, to ensure symmetrical output swing. Also, the Sallen-Key low-pass filter is used to realize an eighth-order Butterworth filter. The whole circuit is verified by HSPICE simulation based on the MOS model parameters of TSMC 0.18 μm 1P6M (1 Poly 6 Metal) process. The obtained bandwidth is 25.919 kHz.
By observing the simulation result, it shows that the equivalent output noise power spectral density of the whole circuit is effectively reduced since the chopper stabilized techniques is adopted in this design. So the noise impact is decreased successfully.
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