On the design of CMOS current conveyors

A general method for converting an operational amplifier (op-amp) into a se cond-generation current conveyor (CCII) is described in this paper. This me thod applies to a wide variety of types of op-amps. It is illustrated by an in-depth analysis of a current conveyor constructed from a simple two-stag e op-amp with compensation. The method circumvents the use of more transist ors between the power rails than those inherent in the op-amp used, and the resulting current conveyors have a low-impedance X input, high-impedance Y input, and a unity current transfer between the X and Z nodes over the ent ire range from do to approximately the unity-gain frequency of the op-amp. It is shown that several other CCII designs that have been presented in the literature can also be considered as applications of this design approach, thereby demonstrating the generality of this method. Theoretical results a re confirmed using HSPICE.