Filter Design Based On Current Conveyor

Compared with voltage-mode circuit, current-mode circuits have advantages of high-frequency property, wider dynamic range and lower power consumption. Current conveyor(CC) was the most powerful and widely used standard module in current-mode circuit, which becomes the cell in current-mode circuit design. At present, most researches are about the first generation current conveyor(CCⅠ) and the second generation current conveyor(CCⅡ),while the third generation current conveyor(CCⅢ) little. What’s more, the third generation current conveyor filter was rarer.In this paper, the principle of current conveyor and the methods of design filter are studied. Firstly, the development situation of current-mode circuit in recent years was introduced. Then, starting from the principle of CCⅠ, CCⅡ was draws out and its input-output characteristics were analyzed in theory. Because of the CCⅡ only has a singe output and its current direct and feedback cannot be realized meanwhile, if carry out current feedback will breach the high output resistance, so CCⅢ was drawn out. On the basis of traditional filter design, comments were made for designing method of filter based on current conveyor. A new method for the design of high-order voltage-mode low-pass filter based on CCⅡ+is presented. The systematic design formula is derivative. A sixth-order Butterworth low-pass filter is designed based on the proposed method and simulated in PSPICE. A systematic method of designing for Nth-order voltage-mode multiple-loop feedback low-pass filter based on CCⅡ+is presented. Different finds of Nth-order low-pass filter structure are obtained by this method. According to the characteristic of CCⅢ, a filter network was designed using the model of two-part networks. A current-mode second-order universal filter based on CCⅢ is presented. The circuit consists of two CCⅢs and four passive elements, it can perform the functions of second-order low-pass, band-pass and high-pass, all of passive components are grounded and can be easily cascaded to produce higher-order filter, and it has very low passive and active sensitivities. A systematic design method for current-mode Nth-order universal filter based on CCⅢ is presented. The systematic design formula derivation is performed. The Nth-order high-pass, low-pass and band-pass filters are obtained by this method. The circuit consists of N CCⅢ+s and2N passive components. As an example, a second-order universal filter is designed by the systematic design method, and passive and active sensitivities of the circuit are analyzed. Result shows that the circuit has low passive and active sensitivities.