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Differential LC voltage-controlled oscillator

  • US 6,469,587 B2
  • Filed: 12/04/2000
  • Issued: 10/22/2002
  • Est. Priority Date: 12/04/2000
  • Status: Expired due to Term
First Claim
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1. A voltage-controlled oscillator comprising:

  • a voltage-to-voltage converter configured to adjust a gain of an input differential voltage and to shift a DC level of the differential input voltage to generate a differential control voltage, the voltage to voltage converter comprising;

    a voltage-follower amplifier is configured to provide a relatively high input impedance to a circuit providing the differential input voltage;

    a first differential amplifier stage is configured to shift the DC level of the differential input voltage; and

    a second amplifier stage is configured so as to provide a predetermined overall gain of the voltage-to-voltage converter, the overall gain including a gain of the voltage-follower amplifier and the first differential amplifier stage, wherein the voltage to voltage converter applies the overall gain to the differential input voltage; and

    a differential VCO comprising;

    an inductance/capacitance (LC) tank circuit having a pair of varactors configured back-to-back, wherein capacitance of the back-to-back varactors contributes to capacitance of the LC-tank circuit; and

    a differential amplifier having its differential output terminals coupled through the LC-tank circuit to its differential input terminals in a feedback path configuration, wherein the VCO receives the differential control voltage applied across each varactor to set capacitance of each varactor; and

    the differential amplifier generates an oscillating waveform in the feedback path at a frequency that is a function of the capacitance and inductance of the LC-tank circuit.

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