Study On Fully-integrated Continiuous-time Filter Based On CFA

With the development of electronic technology, many circuits and systems need to distinguish the signals with different frequencies in order to make the filter designing theory perfect. In recent years, because of the good accuracy of bandwidth and any other properties, the current-mode integrated continuous time filters based on current-mode and current-technology develop rapidly. The current-mode filters have the ability to use lower source standard but not to influence the signal processing ability. Because of the above reasons, the current-mode filters lay a foundation for the microminiaturization of the integration system and further lower power loss.At first,the development of the filter was introduced in this paper,and then introduce the types an characteristics of the morden analog integrated filters.combining with the domestic and foreign research on the current status of the filters,we started the analysis of the current feedback operational amplifier.Current Feedback Operational Amplifier (abbreviation: CFA) also is called transimpedance operational amplifier,it has very good Performance advantage,CFA has good dynamic property that has broken through some traditional baffling problems for conventional VFA Puzzle,have obvious Practical and theoretical value,the huge interest that has aroused circuit and systematic academic circles.The theoretics and synthesis of differential CFA integrator and its filter circuit is studied in this paper. Firstly,with the topology and model circuit, the principle of CFA is introduced in this paper. the characteristics and virtue of ideal CFA is analyzed , the circuit model and model parameter of CFA is introduced .By the studies of CFA integrator circuit, a novel differential CFA lossless integrator and lossy integrator is designed. A differential integrator implemented using current feedback amplifiers(CFAs)is presented in this paper.the resulting integrator is stable and does not employ a capacitor in the negative feedback path of the CFA for its operation.Based on CFA, a universal second-order filter is proposed and a low-pass, band-pass and high-pass filter which can be simultaneously realized is put forward in this thesis with no need for changing the topology of the circuit. Finally, a low-pass use both differential CFA lossless integrator and lossy integrator is designed, and the filter is comparatively content.