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Time constant automatic adjustment circuit for a filter circuit

  • US 4,818,903 A
  • Filed: 07/17/1987
  • Issued: 04/04/1989
  • Est. Priority Date: 07/18/1986
  • Status: Expired due to Term
First Claim
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1. An automatic adjustment circuit for adjusting a filter circuit, the filter circuit having a time constant, the adjustment circuit adjusting the time constant and receiving a reference frequency signal, said adjustment circuit comprising:

  • oscillation means for generating an oscillation signal, said oscillation means including a time constant variable filter and a feedback amplifier connected to said variable filter for positive feedback; and

    means for detecting a difference in phase between said reference frequency signal and said oscillation signal and generating a control signal for automatically adjusting the time constant of the filter circuit.

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