| 摘要 |
In a voltage controlled oscillator, a voltage controlled oscillating part includes a resonance circuit, a differential amplifying circuit and an active load. The resonance circuit generates a resonance signal. The differential amplifying circuit feeds back the resonance signal from the resonance circuit and outputs two oscillation signals having a phase difference of 180°. The active load controls gain of the oscillation signals generated in the differential amplifying circuit. Further, an automatic amplitude controlling part converts the oscillation signals into a direct voltage and compares the direct voltage with a preset reference voltage to output a control voltage for determining a resistance value of the active load. The invention effectively adjusts amplitude of the oscillation signals outputted and reduces phase noise resulting from noise components induced by current source in case of switching of the differential amplitude circuit. |
