| 摘要 |
PURPOSE:To attain a quick switching without the need of externally fitted parts such as a switch and a relay by providing a switching circuit in the interior of an A-D converter IC and switching an action state and a standby state with the aid of a clock from the outside. CONSTITUTION:When the inverse of a chip enable signal CE is supplied to the terminal 28 of a bias circuit 14, a diode 26 is turne on at a low level, and the base potential of a transistor 21 comes to a low level. In the transistor 21 its base current does not flow to turn off the transistor 21, and simultaneously a transistor 22 is also turned off. In that case a current does not flow in a diode 27, and a connection point between the collector of a transistor 23 and the base of a transistor 24 is kept at a high potential. Consequently the transistors 23 and 24 are simultaneously turned on, an appropriate base current is supplied to switching transistors 351, 352, ... in comparators 121, 122,.... As a result the transistors 351, 352,... are turned on to bring the comparators 121, 122,...operable, and a video signal is sampled.
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