Flash analog-to-digital converter with logarithmic/linear threshold

Abstract

A plurality of equally spaced terminals may be disposed at a side edge of a substantially uniformly resistive thin film. A reference potential (e.g. ground) may be applied to the second side of the film. An energizing voltage may be applied at the juncture between the first side edge and a particular one of the top and bottom edges of the film. In this way, the successive terminals receive voltages with a logarithmic relationship relative to the terminal positions. When a linear relationship of voltages is desired at successive terminals in a low range, no reference potential is applied to the second side edge of the thin film. Instead, the other one of the top and bottom edges may receive the reference voltage. Alternatively no reference voltage may be applied and terminals indicating the linear voltages may be disposed at such other edge. Each of a plurality of comparators providing an output indicative of the input voltage receives an input voltage and the voltage at an individual one of the successive terminals. The voltages in the logarithmic portion of the thin film may be calibrated by a circuit including a capacitance to indicate voltage deviations from the logarithmic relationship. The successive terminal voltages in the linear portion of the film may be calibrated by the capacitance circuit and a constant current source to indicate voltage deviations from the linear relationship.