Patent ID: 6680655
Filing Date: 2004-01-20
Classification: H03B

Abstract:
A voltage controlled oscillator (VCO) comprising:a resonant tank circuit; cross-coupled first and second transistors connected to the resonant tank circuit and having a pair of commonly connected terminals; a tail circuit connected to the commonly connected terminals for providing bias current to the VCO wherein the tail circuit comprises a plurality of switches connected in parallel; and a control circuit connected to the plurality of switches in the tail circuit, the control circuit adapted to generate a digital control word in response to a measured system parameter sensitive to the performance level of the VCO, the digital control word comprising a plurality of bits coupling respectively to the plurality of switches and the value of each bit determining whether the corresponding switch is on or off thereby adjusting the bias current provided by the tail circuit to maintain the oscillation amplitude of the VCO within a predetermined range.