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Sigma-delta analog to digital converter

  • US 5,392,039 A
  • Filed: 05/21/1992
  • Issued: 02/21/1995
  • Est. Priority Date: 06/01/1991
  • Status: Expired due to Fees
First Claim
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1. An analog-to-digital converter having an input for receiving analog signals, the converter comprising:

  • quantizing means for producing a digital output of the converter;

    first combining means for combining the analog input with a first feedback signal derived from the digital output and producing a first combined signal; and

    filter means for filtering the first combined signal, the filter means including;

    at least two filter circuit stages each comprising a parallel resonant circuit which is not connected to a respective phase-modifying series resistive means; and

    second combining means for combining an output from the filter means after a final filter circuit stage of the filter means with a second feedback signal derived from the digital output,said filter means producing a signal for input to the quantizing means;

    wherein said second combining means comprises a summing node.

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