Research And Design Of The CMOS Integrated SC Filter Based On The Biquad

The design of the switched capacitor filter is one of the research focuses in circuit and system. With the development of the very large scale integrated circuit technology, people' s attention is more and more concentrating on the miniaturization of the large component including the filters. The switched capaci tor filter is the counterpart of the continue time analog filter' s sampling, it is more adapted to the miniaturization of the circuit and can realize the higher accuracy transfer function, especially the design of the CMOS integrated SC filter based on the biquad have advantage of high accuracy, small area, low power consumption, simple architecture and easy to debug. It has important academic and practical means of the SC filter' s research and design.The paper first reviews the research background and actuality of the filter' s design in china and other country, introduces the meaning of the project and the work of the paper, narrates the theory of the switched-capacitor network and the basic switch building blocks, analyses the related factors of the design of SC filter. Such as the selection of the architecture, the trade off of the opamp' s gain, bandwidth, phase margin, slew rate and setting time, the effect of the switch' s on resistor, how to reduce the charge injection and the clock feed-through, the power consumption and the selection of the sampling frequency and so on.Based on the analysis of the theory, the paper put forward the method of the analysis and design of the SC filter by the discrete time signal method using the basic switch blocks combined with the fabrication convenience, mature technology, low power consumption,higher integrated CMOS process. This paper introduced the design of the sixth order bandpass SC filter with the bandwidth of the 100k by cascading, the procedure including compiling M file by the popular tool of the MATLAB to simulate the system, and realizing the advanced bandgap current circuit, the one stage folded cascade opamp with improved large swing bias, two no-over kipping clock circuit and switched capacitor network to design biquad. In the basic of the holding the characteristic of the circuit, we reduced the capacitor' s spread to increased the accuracy of the transfer function by dynamic range scaling and capacitor scaling. The filter can use in the low frequency transceiver and the base-band circuit and have higher practicability.Finally, the paper gives the conclusion of the work and put forward the more work of the study of the SC filter.