Oppositely-Coupled PMOS 커패시터 쌍의 비선형성을 고려한 디지털로 제어되는 발진기 설계

Contrary to conventional digitally controlled oscillator(DCO), frequency inversion is observed in a DCO using oppositely-coupled pMOS capacitor pairs. It is due to the nonlinearity of the capacitor. In this work, effect of the capacitor nonlinearity on oscillation frequency is analyzed and applied to the DCO to explain the frequency inversion. A 4.8 GHz digitally controlled oscillator for verifying the method is fabricated with 0.18-μm CMOS process and measured.