A 5.5GHz, 8mW, LC tank CMOS VCO with optimal phase noise performance

5.5 GHz LC VCO is fabricated using 0.18 um CMOS process. And this paper presents the phase noise performance dependence on the tail current source transistor in standard CMOS technology. The LC VCO has the minimum point of frequency variation and the optimal selection of tail current at maximum 2nd-order generation can achieve good phase noise performance. By optimizing the tail current, we have achieved phase noise, -90 dBc/Hz at 100 kHz offset.