| 摘要 |
PURPOSE:To reduce power consumption by separately providing power sources of source followers of the initial and second stages, and reducing the voltage of the follower of the second stage lower than the voltage of the follower of the initial stage. CONSTITUTION:In case of VDD1-Vs5>=VFD-Vss-Vth where the source voltage of a transistor 5 is represented by Vs5, the transistor 5 is operated in a saturated range, where VFD is the potential of NFD and Vth is the threshold voltage of the transistor 5. Since the maximum of the FFD is VR, in case of VDD1>=VR-Vth, the source follower of the initial stage is normally operated in a saturated range. Vs5 becomes the gate voltage of a transistor 6, but since VS5<VFD-Vth is satisfied, the input voltage of the follower of the second stage becomes lower than that of the first stage. In order that the follower of the second stage may operate in a saturated range, VDD2-Dout>=Vss-Dout-Vth must be satisfied. Accordingly, VDD2>VR-2.Vth is satisfied, and the VDD2 can be reduced lower than the VDD1. Thus, a CCD output circuit having small power consumption can be obtained.
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