| 摘要 |
An active inductor oscillator includes a tank circuit for generating a first differential signal, a common-mode inverting differential buffer for generating a second differential signal in response to the first differential signal, and an integrating circuit for generating a third differential signal in response to the second differential signal. The third differential signal is applied to the tank circuit, and lags the first differential signal. A differential transistor pair in the tank circuit provides active inductance in response to the third differential signal, and a cross-coupled transistor pair in the tank circuit provides negative resistance that amplifies the first differential signal in response to the first differential signal. Currents through the tank circuit, buffer, and integrating circuit are essentially identical to one another and move in unison with an externally applied reference current that controls the oscillation frequency. As a result, the oscillator can achieve a wide range of oscillation frequencies. The buffer adds 180 degrees of phase shift to the common-mode loop, thereby providing negative common-mode feedback that prevents lock-up. The tank circuit, buffer and integrating circuit use differential transistor pairs that reduce phase jitter due to external common-mode noise sources. |
