Applications of current-copier circuits

Abstract

The term “current copier” was first used by one of us, for whom analog signal processing was the main focus. In this case, the name arose from the system-level requirement for a circuit capable of distributing multiple copies of an input, output, or state variable in current form within a current-mode discrete-time analog filter. Groeneveld et al. use the term “calibration circuit”, indicative of the function performed by the cell in their monolithic current-mode D/A converter. The algorthmic A/D converter reported by Nairn and Salama employs a “current matching” circuit as its essential feature, ideally eliminating dependence on the matching or ratioing of any circuit components. These multiple geneses suggest that the time has come for this circuit, for reasons of both technological feasibility and usefulness of function. Further, the variety of names is a clear indication of the variety of systems to which a cell capable of copying a current can be applied. In this chapter, we review applications of “current copier” circuits, and suggest new ones. Deferring a discussion of scientific nomenclature to one more capable we will use the name “current copiers” in this chapter because (a) it is the name used in the first publication on this subject tιl and (b) we feel it is the most comprehensively descriptive of the circuit operation and use.