ANALOG UNIVERSAL ACTIVE DEVICE - THEORY, DESIGN AND APPLICATIONS

This paper introduces the concept of what we call analog Universal Act ive Device (UAD), as a step forward from Operational Amplifiers and ot her recently proposed active devices. The model for such a device is n othing but a two port classically known as Nullor. To obtain practical implementations of the UAD, or Nullor, a unified aproach is proposed. The basis of the approach is the use of a single cell consisting of a voltage and current buffer, also known as negative second-generation Current Conveyor (CCII-). We obtained the four most simple implementat ions for the UAD as a paradigm of more complex ones. Non ideal effects of these practical implementations are theoretically analysed, partic ularly parasitic impedances associated to the interconnections of the CCII- cells, and then their influence in some simple amplifier stages. It is demonstrated that while any UAD implementation can be used in a given application, its performance is strongly dependent on its imple mentation. Also, a novel floating structure for a General Impedance Co nvener (GIC) type impedance, containing two UADs, is suggested. Simula tion results are given supporting the ideas presented here.