Solid-state image pickup device and clamp control method therefor
a technology of solid-state image and control method, which is applied in the direction of color television details, television system details, television systems, etc., can solve the problems of difficult miniaturization of camera systems using such an ic chip, noise contamination from the signal processing board (or signal processing ic), and power source voltage or gnd contamination, etc., to suppress the effect of noise on image pickup signals, reduce the effect of noise on the gain control amplifier, and suppress the effect of nois
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first embodiment
[0053]FIG. 2 is a block diagram showing the construction of an analog FE of a solid-state image pickup device according to the present invention.
[0054]The analog FE1 is designed so that a voltage-current converting circuit (attenuating amplifier) 36 is added to the construction of the conventional analog FE shown in FIG. 15, and a CDS circuit 3, an AGC circuit 4, an LPF circuit 5, a DRV amplifier 6, etc. are the same as shown in FIG. 15. Further, capacitors 9, 15, etc. connected to the analog FE1 from the outside are the same as shown in FIG. 15. In this case, the external capacitor 9 corresponds to the first capacitance element described above.
[0055]As in the case of FIG. 15, the clamp circuit 18 is equipped with a feedback loop 18A, a switch 18B, a reference voltage source 11 and an OP amplifier (operating means) 12, and a voltage-current converting circuit 36 is equipped as gain control means between the switch 18B of the feedback loop 18A and the AGC circuit 4.
[0056]In the clamp...
second embodiment
[0066]FIG. 4 is a block diagram showing the construction of an analog FE of a solid-state image pickup device according to the present invention.
[0067]The analog FE of this embodiment has the same basic construction as shown in FIG. 2. However, this embodiment is different from the embodiment of FIG. 2 in that a capacitor (second capacitance element) 41 for holding the voltage of the feedback loop 18A is equipped on the feedback loop 18A input to the OP amplifier 12, and a switch 18B is equipped at the upstream side of the capacitor 41 (at the output terminal (7) side). That is, in this embodiment, even when the switch 18B is set to “OFF” state, the capacitor 15 connected to the external connection terminal 14 is prevented from being kept under the floating state, so that the effect of various kinds of noises contaminated from the capacitor 15 connected to the external connection terminal (hum noises, external diving noises, power source / GND noises) can be suppressed. This correspon...
third embodiment
[0069]FIG. 5 is a block diagram showing the construction of an analog FE of a solid-state image pickup device according to the present invention.
[0070]In this embodiment, a capacitor 42 is equipped in the analog FE1 in place of the capacitor 15 connected to the external connection terminal 14 shown in FIG. 2. This circuit construction makes the external connection terminal unnecessary, and brings the following effects.
[0071]A first effect resides in that it would be unavoidable that any noise is contaminated from the external connection terminal itself if the external connection terminal is led out, however, this embodiment can prevent contamination of such noises.
[0072]A second effect resides in that if a capacitance element having a large capacitance value of about 0.1 μF to 10 μF is equipped to the external terminal, the volume of the capacitance element would be large and thus it would be difficult to miniaturize the overall construction of the system, however, this embodiment c...
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