| 摘要 |
PROBLEM TO BE SOLVED: To obtain a video signal clamp circuit insusceptible to APL variation. SOLUTION: Current of a clamp transistor 4 is detected by a current mirror circuit 8 and converted into a voltage by a resistor element 9. Its detection voltage is applied to a resistor element 10 at one end of a series circuit of the resistor elements 10 and 11. Since a clamp reference voltage Vc has been applied to the resistor element 11 at the other end of the series circuit, the clamp reference voltage Vc on which the detection voltage of the resistor element 9 is superposed appears at the series connection end of the series circuit connected with the base electrode of the clamp transistor 4. In other words, the clamp reference voltage Vc increased or decreased by the detection voltage is applied to the base electrode of the clamp transistor 4. Consequently, voltage variation of a sink chip resulting from voltage variation between base-emitter caused by current variation of the clamp transistor 4 during APL variation can be suppressed. COPYRIGHT: (C)2007,JPO&INPIT
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