low pass filter circuit

Abstract

The invention discloses a low-pass filtering circuit. The low-pass filtering circuit comprises a low-noise switched capacitor low-pass filtering circuit, a low-noise analog low-pass filtering circuit, an oscillator circuit and a frequency dividing circuit, wherein the oscillator circuit produces high frequency clock CLOCK(H) with frequency of f(h), the high frequency clock CLOCK(H) is divided by the frequency dividing circuit to produce low frequency clock CLOCK(L) with frequency of f(l), and two clocks phi 1and phi 2 with two phases not overlapping are produced. The low-noise analog low-pass filtering circuit and the low-noise switched capacitor low-pass filtering circuit are in series connection. The low-noise analog low-pass filtering circuit filters out burrs introduced by a switch of the low-noise switched capacitor low-pass filtering circuit. The high frequency clock CLOCK(H) with frequency of f(l) produced by the oscillator circuit is regarded as chopped wave frequency of a chopped wave operational amplifier of the low-noise analog low-pass filtering circuit and the low-noise switched capacitor low-pass filtering circuit. The monolithic integration low-pass filtering circuit is simple in structure, very low -3dB corner frequency can be achieved according to need, and meanwhile a filter achieves very low low-frequency noise and imbalance, and the accuracy of filtering is improved.

Description

technical field [0001] The invention relates to an analog integrated circuit technology, especially a technology suitable for improving low-frequency noise of a low-pass filter circuit. Background technique [0002] Compared with the filter circuit composed of separate devices, the monolithic integrated filter has the advantages of small size, low power consumption and reduced number of components in system applications. The traditional monolithic integrated active low-pass filter circuit cannot provide a very low -3dB corner frequency because of the very large capacitor or resistor area. [0003] Although the capacitor area and resistance value can be greatly reduced by using the switched capacitor filter technology, the turning off and closing of the switch will introduce glitches, and the low frequency 1 / f noise cannot be effectively eliminated. The Chinese Patent Publication No. is CN101388596A for the low-pass filter patent. By adopting the switched capacitor filter te...

AI Technical Summary

Problems solved by technology

However, this invention cannot effectively eliminate the low-frequency 1 / f noise and the offset introduced by the process, which affects the filtering accuracy

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