| 摘要 |
PURPOSE:To prevent step-out from being generated even when the level of clock components declines-by selecting the output voltage of an eye detector by a control voltage switching device when the level of the clock components is lower than prescribed level. CONSTITUTION:The respective output of amplifiers 5 and 6 is synthesized after being passed through nonlinear circuits 7 and 8 and the clock components are extracted through a, band-pass filter 11. The clock components are inputted to a phase comparator 12 and compared with the output of a VCO 13. The level of the clock components is detected by a level detector 16 and the control voltage switching device 17 is switched and operated corresponding to the detected level of the clock components. By the switching operation of the switching device 17, the output voltage of the comparator 12 or the output voltage of the eye detector 15 is selected as the control voltage of the VCO 13. The switching device 17 selects the output voltage of the comparator 12 as the control voltage of the VCO 13 when the level of the clock components is higher than a prescribed level and selects the output voltage of the detector 15 when it is lower than the prescribed level. |
