A 2.2 GHz CMOS VCO with inductive degeneration noise suppression

A 1.4 V, 9 mA monolithic LC-tank voltage-controlled oscillator (VCO) fabricated in a standard 0.35 /spl mu/m CMOS process is presented. The VCO is tunable between 2.0 GHz and 2.37 GHz, and displays a phase noise between -140 dBc/Hz and -138 dBc/Hz at a 3 MHz offset frequency across the whole tuning range. This low phase noise is achieved through the use of an on-chip LC filter and an off-chip low frequency inductor, which totally remove the noise of the tail current source. The phase noise improvement due to the off-chip inductor is between 2 dB and 6 dB, increasing with higher oscillation frequencies.