| 摘要 |
PROBLEM TO BE SOLVED: To provide a voltage-controlled oscillator that prevents a degradation of phase noise even if an output is variable over a wide band, and a PLL circuit using the voltage-controlled oscillator.SOLUTION: The PLL circuit comprising a PLL section 2 for outputting a signal depending on a phase difference between a reference signal and an output signal, and a voltage-controlled oscillator 4 fed with a control voltage generated on the basis of the signal output from the PLL section 2 and adapted to oscillate a signal of a frequency depending on the control voltage includes determination means, comprising an integrator 5 and a determination section 6, for generating a switching signal to switch the frequency band of oscillation on the basis of an unlocking detection signal and a three-state output signal from the PLL section 2, and sending the generated switching signal to the voltage-controlled oscillator 4. |
