Patent ID: 7057469

Claim:
A differential negative resistance generator for providing negative resistance to a differential resonator of a differential voltage controlled oscillator (VCO), comprising: first and second active devices, each having first and second current terminals and a control terminal; first and second current sinks, each coupled to a corresponding one of said second current terminals of said first and second active devices; and a capacitive degeneration circuit coupled to said first and second active devices and operative to cancel at least a portion of extra capacitance of the differential negative resistance generator applied to the differential resonator, the capacitive degeneration circuit including at least one capacitive device coupled between said second current terminals of said first and second active devices that has a capacitance value selected so that the negative resistance generator has only negative resistance and the reactive component of impedance is eliminated, and further comprising first and second current sinks, each coupled to an emitter of a respective one of said first and second active devices, wherein said firs and second current sinks each comprises: a current sink transistor having an emitter, a collector coupled to an emitter of a respective one of said first and second active devices, and a base coupled to a bias voltage.