| 摘要 |
PROBLEM TO BE SOLVED: To shorten the acquisition time without deteriorating distortion characteristics in a tracking mode. SOLUTION: The switched emitter follower circuit is switchable to the tracking mode for making an output voltage follow an input voltage and a hold mode for holding the output voltage, and is equipped with: a transistor wherein an input voltage terminal and a constant current source are connected through a switch to a base, an output voltage terminal and a variable current source are connected to an emitter, and a power supply voltage is applied to a collector; a capacitor wherein the power supply voltage is applied to one end and the other end is connected to the output voltage terminal; and a control part for controlling the switch and the current value of the variable current source. When switching from the hold mode to the track mode, the control part switches the switch from OFF to ON, also switches the current value of the variable current source from 0 to a first value, and switches the current value to a second value larger than the first value after the lapse of the prescribed time. COPYRIGHT: (C)2011,JPO&INPIT
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