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High performance switched-capacitor filter for oversampling sigma-delta digital to analog converters

  • US 6,268,815 B1
  • Filed: 03/03/2000
  • Issued: 07/31/2001
  • Est. Priority Date: 06/15/1999
  • Status: Expired due to Term
First Claim
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1. A filter for oversampling Sigma-Delta digital to analog converter circuits capable of accommodating different digital subscriber line applications, comprising:

  • a SINC filter that decimates a digital data input signal by a predetermined factor of an over-sampling ratio utilized by a Sigma-Delta modulator and further uses positive and negative reference voltages in combination with bottom-plate switched-capacitors to avoid a signal dependent load on reference buffers;

    a switched-capacitor biquad filter having a programmable cut-off frequency which tracks the over-sampling ratio; and

    a sample and hold buffer.

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