| 摘要 |
PROBLEM TO BE SOLVED: To provide a voltage-controlled oscillator having an automatic amplitude control function which has excellent phase noise characteristics, by eliminating the phase noise caused by a current source by controlling a gain, by adopting active load in place of the current source. SOLUTION: A voltage-controlled oscillator has an automatic amplitude control function, 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 and outputs two oscillation signals, having a phase difference of 180°; and the active load controls gain of the oscillation signals generated in the differential amplifying circuit. Furthermore, an automatic amplitude control part is included to convert the oscillation signals into a direct voltage, compares the direct voltage with a preset reference voltage and determine the resistance value of the active load. The invention effectively adjusts the amplitude of the oscillation signals outputted and reduces the phase noise resulting from noise components induced by current source in case of switching of the differential amplitude circuit. COPYRIGHT: (C)2007,JPO&INPIT
|
