| 摘要 |
AN AUTOMATIC FINE-TUNING CONTROL (AFT) VOLTAGE GENERATING CIRCUIT IS PROVIDED IN WHICH A GENERAL-PURPOSE INTEGRATED CIRCUIT FOR AN INTERMEDIATE FREQUENCY (IF IC) IS USED, WHICH IS CAPABLE OF EASILY DETECTING A LOW LEVEL POINT IN A SIMPLE MANNER WITHOUT INCREASING THE MANUFACTURING COST. THE AUTOMATIC FINE-TUNING CONTROL VOLTAGE GENERATING CIRCUIT INCLUDES A SURFACE-ACOUSTIC-WAVE (SAW) FILTER (1) FOR FILTERING AN INTERMEDIATE VIDEO FREQUENCY SIGNAL; AN IF IC (2), CONNECTED TO THE SAW FILTER, FOR DETECTING THE FILTERED INTERMEDIATE VIDEO FREQUENCY SIGNAL AND FOR GENERATING AN AFT VOLTAGE; AND A LEVEL SHIFT CIRCUIT (3), CONNECTED TO THE IF IC, FOR SHIFTING THE NON-SIGNAL-TIME LEVEL OF THE AUTOMATIC FINE-TUNING CONTROL VOLTAGE GENERATED BY THE IF IC TOWARD A DIRECTION IN WHICH THE LEVEL IS LOWER THAN AN INTERMEDIATE LEVEL BETWEEN A HIGH LEVEL AND A LOW LEVEL.
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