Solid-State Image Pickup Device and Sampling Circuit

• US 20070222876A1
• Filed: 06/07/2005
• Published: 09/27/2007
• Est. Priority Date: 07/20/2004
• Status: Abandoned Application

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Yonemoto, Kazuya
• Application Number:
  US11/631,796
• Publication Number:
  US 20070222876A1
• Time in Patent Office: Days
• US Class Current: 348/294
• CPC Class Codes: H04N 25/616 involving a correlated sampling function, e.g. correlated double sampling [CDS] or triple sampling
• CPC Class Codes: H04N 25/677 for reducing the column or line fixed pattern noise
• CPC Class Codes: H04N 25/767 Horizontal readout lines, multiplexers or registers
• CPC Class Codes: H04N 25/78 Readout circuits for addressed sensors, e.g. output amplifiers or A/D converters

Abstract

To provide a solid-state image pickup device which prevents the generation of fixed pattern noise having a correlation in a column direction (or a row direction) caused by non-uniformity of a sampling circuit itself. The solid-state image pickup device includes a sampling circuit for sampling a signal from a photodiode. The sampling circuit includes: a clamp capacitor C_CL for transmitting only an AC component of the signal; a sampling capacitor C_SH for holding the signal transmitted via the clamp capacitor C_CL; and a sampling MOS switch M12 for transmitting the signal to the sampling capacitor C_SH or blocking the transmission. A ratio between the clamp capacitor C_CL capacity and the sampling capacitor C_SH capacity is a fixed value determined by a capacity unique to the sampling MOS switch M12.

Claims

1. A solid-state image pickup device comprising a sampling circuit for sampling a signal from a photodiode,

wherein said sampling circuit includes:

a clamp capacitor which is a capacitor for transmitting only an AC component of the signal;

a sampling capacitor which is a capacitor for holding the signal transmitted via said clamp capacitor; and

a sampling Metal Oxide Semiconductor (MOS) switch which is a MOS transistor for transmitting the signal to said sampling capacitor, or blocking the transmission; and

a relation between a capacity of said clamp capacitor and a capacity of said sampling capacitor is determined by the capacity unique to said sampling MOS switch.

2. The solid-state image pickup device according to claim 1,

wherein said sampling MOS switch is connected in series between said clamp capacitor and said sampling capacitor, and

a ratio between the capacity of said sampling capacitor and the capacity of said clamp capacitor is a fixed value determined by the capacity unique to said sampling MOS switch.

3. The solid-state image pickup device according to claim 1,

wherein said clamp capacitor is connected in series between said sampling MOS switch and said sampling capacitor, and

a ratio between (i) a total capacity in the series connection between said sampling capacitor and said clamp capacitor and (ii) a capacity of a column signal line, which transmits the signal, is a fixed value determined by the capacity unique to said sampling MOS switch.

4. The solid-state image pickup device according to claim 2,

wherein the fixed value is approximately equivalent to a ratio between a gate-source capacity and a gate capacity of said sampling MOS switch.

5. The solid-state image pickup device according to claim 1,

wherein said sampling circuit further includes:

a column-selecting MOS switch for turning ON or OFF a connection between said sampling capacitor and an output line, and

a bias voltage application circuit for applying a bias voltage to the output line, and

said bias voltage application circuit changes the bias voltage applied to the output line in synchronization with a control signal for turning turns said column-selecting MOS switch from ON to OFF.

6. The solid-state image pickup device according to claim 5,

wherein said bias voltage application circuit changes the bias voltage based on a proportional coefficient, that is, the value determined by the capacity of said sampling capacitor;

a capacity of said clamp capacitor;

a capacity between the output line and the reference potential; and

a capacity unique to said column-selecting MOS switch.

7. A solid-state image pickup device comprising a sampling circuit for sampling a signal from a photodiode, said device comprising

two of said sampling circuits per a column of photodiodes,

wherein said two sampling circuits are connected to each other in parallel so that a column signal line, which transmits a signal from the column of photodiodes, is a common input,

said sampling circuit includes:

a sampling capacitor which is a capacitor for holding the signal; and

a sampling Metal Oxide Semiconductor (MOS) switch which is a MOS transistor for transmitting the signal to said sampling capacitor, or blocking the transmission; and

a ratio between a capacity of said sampling capacitor and a capacity of the column signal line is a fixed value determined by a capacity unique to said sampling MOS switch.

8. The solid-state image pickup device according to claim 7,

wherein the fixed value is approximately equivalent to a ratio between a gate-source capacity and a gate capacity of said sampling MOS switch.

9. The solid-state image pickup device according to claim 7,

wherein said sampling circuit further includes a column-selecting MOS switch which is a MOS switch for turning ON or OFF a connection between said sampling capacitor and an output line, and when the signal held in said sampling capacitor is outputted to the output line, the column-selecting MOS switch is brought into a conduction state from a non-conduction state, then brought into the non-conduction state again.

10. A sampling circuit for sampling a signal from a photodiode, said circuit comprising:

a clamp capacitor which is a capacitor for transmitting only an AC component of the signal;

a sampling capacitor which is a capacitor for holding the signal transmitted via said clamp capacitor; and

a sampling MOS switch which is a MOS transistor for transmitting the signal to said sampling capacitor or blocking the transmission,

wherein a relation between a capacity of said clamp capacitor and a capacity of said sampling capacitor is determined by a capacity unique to said sampling MOS switch.

11. A sampling circuit for sampling a signal from a photodiode, said circuit comprising:

a sampling capacitor which is a capacitor for holding the signal; and

a sampling MOS switch which is a MOS transistor for transmitting the signal to said sampling capacitor or blocking the transmission,

wherein the ratio between a capacity of said sampling capacitor and a capacity of a column signal line which transmits a signal from the photodiode is a fixed value determined by a capacity unique to said sampling MOS switch.