Design And Application Of Digit Controlled Fully Balanced Second-generation Current Conveyor Circuit

In modern society, fully integrated current-mode continuous-time filters as an important composition have great significance in circuit and systems. It is a very important issue to design digitally programable current-mode filter.In this paper, the essential theory and the classification based on transfer function of programmable filter is introduced. The thesis introduces the development and character of the current-mode circuit, and compares all kinds of current-mode filter, especially the filter based on current conveyor. In this paper, a design method producing balanced current-mode programmable filter is proposed, using digit controlled fully balanced second-generation current conveyor circuit (DFBCCII).The main contents are as follows:(1) A new digital control block (DCB) is proposed, then a digit controlled fully balanced second-generation current conveyor circuit is proposed in this paper. The proposed circuit is well capable of eliminating the common mode (CM) signals because of the differential input and output configurations. The X port parasitic resistor is controllable by digital signal, the input impedance of Y port and output impedance is high. The proposed circuit is consist of MOS devices, so the circuit can be integrated easily. The system is stable. At last, the circuit is simulated by Pspice in order to verify the reliability.(2) A systematic method of designing differential nth-order programble filters with multiple-loop feedback is presented in this paper. The parameter of the proposed filter can be tuned by digital signal. The method can realize filters with different structure by selecting different feedback. This system has a fully balanced structure which can restrain even order harmonic distortion and common mode disturbing signal. The filters have no limitation of the orders, the produced nth-order filters are constructed by n DFBCCIIs and 2n grounded capacitors and have no resistance, all passive components are grounded, so the filters can be integrated conveniently. The sensitivities of the filters are analyzed and the Matlab result is given. The parasitic elements on filters are considered, the filters are not affected by non-ideal characteristic of DFBCCII when frequency is less than 10MHz. The cut-off frequency of the filter can be controlled programable.