| 摘要 |
PURPOSE:To prevent troubles of an application-side circuit even in case of an abnormal input by providing an amplitude limiter in the preceding stage of a voltage control oscillator and limiting the output signal of the voltage control oscillator within a frequency range which is allowable in the application-side circuit. CONSTITUTION:The range of frequency of the input signal which is allowable in an application-side circuit 5 is narrower in comparison with a frequency variable range of a voltage control oscillator 4, and the frequency of the output signal of a reference-side circuit 1 is limited to a certain range in the normal state. The voltage range of the control input of the voltage control oscillator 4 used for phase matching is only a part of the range of voltage which can be inputted to the voltage control oscillator 4. This fact is utilized, and an amplitude limiter 6 is inserted between a low-pass filter 3 and the voltage control oscillator 4 to limit the input voltage range of the voltage control oscillator 4, thereby limiting the frequency of the output signal of the voltage control oscillator within the frequency range which is allowable in the application-side circuit 5. |
