| 摘要 |
PURPOSE:To reduce a setting error in the killer level due to a circuit offset, an irregular gain and the fluctuation in electric wave by setting a direct current voltage to be the reference of the comparison by sample holding the output of a synchronization detector and changing a killer threshold thereof with the fluctuation in a reference potential. CONSTITUTION:The first and the second sample hold circuits 3 sample hole the output of the synchronization detector 1 to capacitors 2-2, 3-2, respectively. The output voltage B of a buffer 4 has a linearity determined by the gain of th synchronization detector 1 and when a burst input is zero, it is the same potential as the output voltage C of a buffer 5. D is a threshold voltage provided by making the output voltage C a reference and the potential difference E to the output voltage of the buffer t is not changed even when the output voltage of the buffer 5 is changed. Accordingly, since a killer control signal is obtained from a comparator 8 at an intersection point of the threshold voltage D and the output voltage B of the buffer 4, a killer level can be freely obtained by varying the potential difference E.
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