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Soft transitions between muted and unmuted states in class D audio amplifiers

  • US 20050083115A1
  • Filed: 10/12/2004
  • Published: 04/21/2005
  • Est. Priority Date: 10/15/2003
  • Status: Active Grant
First Claim
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1. An audio amplifier, comprising:

  • difference circuitry, for generating a difference signal responsive to an input signal and a feedback signal;

    a first comparator, for generating first pulse-width-modulated output pulses responsive to a comparison of the difference signal and a periodic reference waveform;

    a second comparator, for generating second pulse-width-modulated output pulses responsive to a comparison of the difference signal and a periodic reference waveform, the second pulse-width-modulated output pulses complementary to the first pulse-width-modulated output pulses;

    a power stage, for driving an amplifier output responsive to the first and second pulse-width-modulated output pulses;

    a loop filter for filtering a signal corresponding to the amplifier output to produce the feedback signal; and

    common mode ramp voltage circuitry, having an output coupled to inputs of the first and second comparators, for generating a common mode voltage of a first level in a muted mode, and for ramping the common mode voltage from the first level to a zero level responsive to a transition from the muted mode to an unmuted mode.

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