A 80~900MHz CMOS VCO with Tunable AAC Circuit

This paper presents an 80~900MHz LC VCO which is implemented in 0.25-mum CMOS technology. The oscillator adopts a multi-VCO structure and an off-chip LC tank. In addition, a charge-pump automatic amplitude control circuit (AAC) is used to ensure a reliable startup and stable working status without degrading the phase noise performance. And the AAC circuit can be tuned to achieve optimized phase noise performance for different frequency bands. Measurement results show that the phase noise achieves -85dBz/Hz at 10 kHz offset frequency