Low-power, low-phase-noise tuned-input tuned-output VCO with loop gain enhancement

A negative conductance is proposed to compensate for the loss of an auxiliary LC tank at the drain of a conventional tuned-input tuned-output voltage-controlled oscillator (VCO). This conductance enhances the loop gain of the VCO. The DC current flowing through the negative conductance generator is reused by the VCO to save power. The proposed VCO is fabricated in a 0.18 μm 1P6M CMOS process. The measurement results show that the phase noise is -120.5 dBc/Hz at 1 MHz offset frequency from the oscillation frequency of 6.08 GHz while dissipating 1.5 mA from a 1.8 V supply with a FOM of -191.9 dBc/Hz.