| 摘要 |
PROBLEM TO BE SOLVED: To make compatible noise resistance and followup ability by switching plural phase comparators through a PLL circuit while providing them with different sensitivities or changing the sensitivity corresponding to the phase difference of two signals inputted to the phase comparator. SOLUTION: Concerning a horizontal synchronizing reproducing circuit of a PLL system for comparing the output or frequency divided output of an oscillator with a horizontal synchronizing signal, 1st and 2nd phase comparators 1 and 2 are provided. In the case of an input from an antenna, for example, a switch S1 is closed and the 1st phase comparator 1 of the low detection sensitivity and high noise resistant performance is used but in the case of an input from a VTR, a switch S2 is closed and the phase comparator 2 of the high followup performance is used. As a concrete circuit, a pair of transistors having the same potential of emitters are used and when the input of the output or frequency divided output from the oscillator is included in the base voltage of any one transistor, the insertion/non-insertion of resistors to the emitters of paired transistors is switched. |
