A negative gyrator-C for purification of inductors in a differential LC-VCO

摘要

Based on the proposed technique, the negative resistor in a differential LC-VCO is configured to impose a negative gyrator-C across the output. This resolves the need for the inductive source degeneration already used for purification of inductors in a differential LC-VCO. In comparison, while the chip area is almost halved, phase noise at 100 kHz offset is noticeably improved from -95.7 to -100 dBc/Hz at no extra power consumption cost. Moreover, in the curve of phase noise versus frequency an inflection point shows up at the minimal. This feature prevents the conventional sharp degradation of the phase noise while the frequency is tuned and extends its minimum for hundreds of MHz to improve the reliability of design. The application of the proposed technique in design of a low power and low phase noise Giga Hertz-range CMOS differential LC-VCO around 2.9 GHz is illustrated and analysed. Post-layout simulations using CMOS 0.18 μm TSMC RF design kit are used for evaluation and comparison. Using 1.8 Vdc supply, the obtained power consumption, output level and tuning range are 2.6 mW, 2.3 Vpp and 12.4%, respectively.