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Adaptive power line noise filter and switch for audio reproduction equipment

  • US 5,043,686 A
  • Filed: 03/14/1989
  • Issued: 08/27/1991
  • Est. Priority Date: 03/14/1989
  • Status: Expired due to Term
First Claim
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1. An adaptive power line filter for an audio reproduction system, comprising:

  • an input port which may be operably connected to a power line in order to accept an input voltage;

    an output port for outputting an output voltage to a load;

    a variable conductivity element interposed between said input and output ports, wherein the conductivity of said conductivity element varies in accordance with a voltage applied to a gate of said conductivity element;

    a filter network for filtering the input voltage and applying the filtered voltage to the gate of said conductivity element so that the output voltage is a filtered version of the input voltage; and

    ,a feedback network for producing a control signal in accordance with the difference between the output voltage level and a predetermined reference voltage level, the control signal then being applied to the gate of said conductivity element so that the input voltage is filtered less as the output voltage level increases.

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