Theory Of Switched-capacitor In The Audio Spectrum Display

Filter, as a kind of circuit, has a very long history, and is also a necessary part in signal processing. It has born when the electronic circuit was invented;it becomes more and more mature and developed in the course of the circuit's complication and systematization. Nowadays, there are many kinds of theories and circuit models about filters. Each of them is fit for some field of application. In this thesis, we will introduce one kind of them, known as Switched Capacitor Circuits, and some kind of filter structures called Switched Capacitor Filters will be involved here too. Besides these, the math method in the analyses of this theory, some types of classical structure of Switched Capacitor circuits, especially the application of this theory in audio spectrum processing-a chip designed on the base of Switched Capacitor circuits, are all included in this thesis. This chip is designed for the use in audio processing. Considering the characteristic of audio spectrum, the precision of the filters and the jump of the pass-band are the major difficulties we have to face. Fortunately, the Switched Capacitor theory helps us solve these problems. The main function of this chip is to filtrate the input signal with a -3db frequency of 20khz(audio spectrum) first, then divide the spectrum into 7 sub-spectrums, detect the peak value of each sub-spectrum and output. This chip was taped out in August 2005, as a part of the Multiple Project Wafer (MPW), organized by Integrate Circuit Center (ICC ShangHai). The testing chip is on a die with an area of 4mm~2, using a 5V 0.6um CMOS mix-signal technology (double well, double poly, double metal).