Patent ID: 6469587
Filing Date: 2002-10-22
Classification: H03B

Abstract:
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.