Patent ID: 8299862

Claim:
An apparatus comprising: a first circuit of a digitally controlled oscillator (DCO), the first circuit having a loss component; a second circuit coupled to the first circuit, the second circuit comprising: a first cross coupled pair of transistors coupled to the first circuit; and an adjustable reactive component coupled to the first cross coupled pair of transistors, the adjustable reactive component configured to adjust a frequency of an output signal of the DCO, wherein the second circuit is configured to transform a positive impedance into a negative impedance and provide a first negative resistance; a third circuit coupled to the first circuit, the third circuit comprising a second cross coupled pair of transistors coupled to the first circuit, wherein the third circuit is configured to provide a second negative resistance and does not include a reactive component, wherein: an equivalent reactance seen by the first circuit is less than a reactance of the adjustable reactive component, and the second circuit and the third circuit are between the first circuit and a supply.