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A/D converter

  • US 4,978,958 A
  • Filed: 10/11/1989
  • Issued: 12/18/1990
  • Est. Priority Date: 07/20/1989
  • Status: Expired due to Fees
First Claim
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1. A circuit for converting an analog electrical signal to a digital signal comprising:

  • means containing sampling and reference input terminals and an output terminal for comparing said analog signal applied to said sampling terminal with a predetermined D.C. reference level applied to said reference input terminal to generate a first binary level output signal on said output terminal corresponding to said analog signal having a value determined by said comparing means as being greater than said predetermined reference level and a second binary level ouput signal having a value determined by said comparing means as being greater than said predetermined reference level;

    means for applying a predetermined reference level to said reference input terminal of said comparing means, wherein said reference level applying means includes a reference voltage divider circuit including at least two reference resistors connected in series between a D.C. voltage source and ground;

    N switchable resistive networks connected in parallel with at least one of the series resistors in said reference voltage divider circuit, wherein "N" is a positive integer being greater than zero (0);

    means for individually switching each of said switchable resistive networks into and out of electrical connection in parallel with said at least one of the series resistors in said reference voltage divider circuit, wherein each of said N switchable resistive networks includes at least one resistor connected in series with an electrical switch that is controllable to open and close in response to applied binary signals, and each switch being connected to a corresponding control terminal; and

    whereby, the selection of binary signals applied to said N control terminals and monitoring of the binarY output signal from said comparing means provides a combined digital binary output representation of the sampled analog signal value to be at least within R adjacent voltage ranges where R=2N -1.

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