Patent ID: 7449972

Claim:
A voltage controlled oscillator with compensation for voltage supply, temperature, and processing variations, comprising: an oscillation circuit, which outputs an oscillatory signal; a current source, which is coupled to the oscillation circuit at a node to provide an input current to the oscillation circuit; and a variation compensation circuit, which is coupled to both the oscillation circuit and the current source to compensate for the variations and which comprises: a peak detector, which is coupled to the oscillation circuit to generate a peak voltage proportional to the amplitude of the oscillatory signal; a compensating voltage generator, which generates a reference voltage according to the variations for compensating the oscillation circuit; a comparator, which compares the peak voltage with the reference voltage to generate a control voltage; and an amplifier, having a first input terminal that is coupled to the node, a second input terminal that receives the control voltage, and an output terminal that is coupled to a control terminal of the current source.