Analog Universal Active Device: Theory, Design and Applications
This paper introduces the concept of what we call analog Universal Active Device (UAD), as a step forward from Operational Amplifiers and other recently proposed active devices. The model for such a device is nothing 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 implementations for the UAD as a paradigm of more complex ones. Non ideal effects of these practical implementations are theoretically analysed, particularly 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 implementation. Also, a novel floating structure for a General Impedance Converter (GIC) type impedance, containing two UADs, is suggested. Simulation results are given supporting the ideas presented here.
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