Symbolic behavioral model generation of current-mode analog circuits

A novel extended method to approximate the behavioral model of current-mode analog circuits (CMACs) is presented. The nullor is employed to model the behavior of a MOS transistor (MOST) together with its parasitic elements. In a first part, the signal-path (SP) into a CMAC is approached by using the nullor properties. In the second part, the behavioral model associated to each MOST is generated and it is more simple in comparison with the original model. As a consequence, in the third part, an admittance matrix of reduced size is built and used to compute small-signal characteristics of CMACs, where the order is given by the number of SP-nodes minus the number of nullors. The proposed technique is illustrated by computing the fully-symbolic transfer function of a positive second generation current conveyor (CCII+) and compared with Hspice simulation.