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Tuning circuit for an RC filter

  • US 5,625,316 A
  • Filed: 07/01/1994
  • Issued: 04/29/1997
  • Est. Priority Date: 07/01/1994
  • Status: Expired due to Term
First Claim
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1. An electronic tuning circuit for tuning an RC filter circuit, the RC filter circuit including a resistor and a programmable capacitor array, the electronic tuning circuit being coupled externally to the RC filter circuit, the electronic tuning circuit comprising:

  • a reference current source for generating a substantially stable reference current, the reference current source including a bandgap reference for providing a bandgap voltage;

    a reference resistor substantially matched to the resistor, the reference resistor coupled to the bandgap reference for receiving the reference current and transforming the reference current into a voltage signal at a node;

    an analog-to-digital converter coupled between the node and the programmable capacitor array for receiving the voltage signal and providing a digital output to the programmable capacitor array.

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