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This paper proposes a diffenent viewpoint for the usual design of second generation current conveyors (CCIIs) and operational transconductance amplifiers (OTAs). The published papers often deal with the voltage transfer ratios and the current transfer ratios of CCII or OTA circuits. In fact, the output current of a positive or negative current conveyor or an operational transconductance amplifier is invariant with different load irapedances, but the output voltage is not. Also, the transfer admittance function is much more useful than the voltage transfer ratio. On the other hand, the majority of the previous papers just wanted to design a biquad filter using CCIIs or a single CCII+ without paying attention to the use or non-use of feedback currents. This paper tries to design a filter of cascaded biquad filters (which is similar to a filter of cascaded OP-Amp biquad filters). The designed filter can satisfy Butterworth, Chebyshev, Bessel, optimum, and many other type filters of any order. And it is our object of research to keep the whole output current of the CCII+ or OTA of the previous stage to be the input current of the next filter stage. Two first-order filter sections, each of which can result in a third-order filter if connected in cascade with a second-order filter section, are introduced. By using any type of CCII+ or OTA voltage filters and/or CCII+ or OTA circuits, a given stable transfer immittance function can be synthesized. A similar method can be applied to Synthesizfe stable rational transfer functions of operational amplifier circuits. Using discrete components, we can prove the transfer functions of the new configuration for CCII+ or OTA filters by experiments. Meanwhile, the properties of the filters are like those of the implementation of integrated circuits. The sensitivities of the passive and active components of the circuits are discussed. This paper proposes a universal active filter with the same type of transfer admittance function and current transfer ratio by using a single CCII+, and one similar filter by using a single OTA. The traditional generalized immittance converters (GICs) and the four kinds of the basic dependent sources can be synthesized by CCII-and resistors and capacitors. Moreover, a simple small signal equivalent circuit of a CCII+ which can be simulated by the program PSPICE is suggested.
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