Solid-state imaging apparatus and sampling circuit
A solid-state imaging apparatus which prevents fixed pattern noise from occurring is provided, the 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 imaging apparatus comprises a sampling circuit in which a signal from a photodiode PD is sampled. And, the sampling circuit includes: a sampling capacitor C SH for holding the signal from the photodiode PD; a sampling MOS switch M 12 which (i) transmits the signal from the photodiode PD to the sampling capacitor C SH , or (ii) blocks the transmission; and a damping capacitor C DS connected to (i) one of a source electrode and a drain electrode of the sampling MOS switch M 12 which is located closer to the sampling capacitor C SH and (ii) a gate electrode of the sampling MOS switch M 12.
1. A solid-state imaging apparatus comprising a sampling circuit in which a signal from a photodiode is sampled,
wherein said sampling circuit includes:
a sampling capacitor for holding the signal;
a sampling Metal Oxide Semiconductor (MOS) switch, said sampling MOS switch being a MOS transistor that (i) transmits the signal to said sampling capacitor, or (ii) blocks the transmission of the signal to said sampling capacitor;
a first damping capacitor connected to (i) one of a source electrode and a drain electrode of said sampling MOS switch, the one electrode being connected to said sampling capacitor and (ii) a gate electrode of said sampling MOS switch; and
a clamp capacitor connected to one of the source electrode and the drain electrode of said sampling MOS switch.
2. The solid-state imaging apparatus according to claim 1 ,
wherein a capacity of said first damping capacitor is expressed by at least one of (i) a capacity between the source electrode of said sampling MOS switch and a reference potential, (ii) a capacity between the drain electrode of said sampling MOS switch and the reference potential, and (iii) a specific capacity of said sampling MOS switch.
3. The solid-state imaging apparatus 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 second damping capacitor, the second damping capacitor being connected to (i) one of a source electrode and a drain electrode of said column-selecting MOS switch, the one electrode being connected to said sampling capacitor and (ii) a gate electrode of said column-selecting MOS switch.
4. The solid-state imaging apparatus according to claim 3 ,
wherein a capacity of said second damping capacitor is expressed by at least one of (i) a capacity between the source electrode of said column-selecting MOS switch and a reference potential, (ii) a capacity between the drain electrode of said column-selecting MOS switch and the reference potential, (iii) a specific capacity of said column-selecting MOS switch, and (iv) a specific capacity of said sampling MOS switch.
5. The solid-state imaging apparatus according to claim 3 ,
wherein said sampling circuit further includes a bias voltage application circuit in which a bias voltage is applied to the output line, and
in said bias voltage application circuit, the bias voltage to be applied to the output line is changed in synchronization with a control signal that turns off said column-selecting MOS switch.
6. The solid-state imaging apparatus according to claim 1 ,
wherein said sampling circuit further includes:
a clamp voltage application circuit in which a clamp voltage is applied to said clamp capacitor, and
the signal transmitted from the photodiode is correlated double sampled.
7. The solid-state imaging apparatus according to claim 1 ,
wherein said sampling circuit is one of two sampling circuits per one column of photodiodes, and
the two sampling circuits are connected to each other in parallel so that one column signal line can be used for a common input, said column signal line transmitting a signal from the one column of photodiodes.
8. The solid-state imaging apparatus according to claim 7 ,
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
when the signal held in said sampling capacitor is outputted to the output line, said column-selecting MOS switch is brought into a conduction state from a non-conduction state, and then brought into the non-conduction state again.
9. The solid-state imaging apparatus according to claim 1 ,
wherein said first damping capacitor is made up of (i) one of a source electrode and a drain electrode of said sampling MOS switch, the one electrode being connected to said sampling capacitor, (ii) a gate electrode of said sampling MOS switch and (iii) a gate oxide film of the sampling MOS switch sandwiched between the source electrode and the drain electrode of said sampling MOS switch.
10. A sampling circuit in which a signal from a solid-state imaging device is sampled, the sampling circuit including:
a sampling capacitor for holding the signal;
a sampling MOS switch, said sampling MOS switch being a MOS transistor that (i) transmits the signal to said sampling capacitor, or (ii) blocks the transmission of the signal to said sampling capacitor;
a first damping capacitor connected to (i) one of a source electrode and a drain electrode of said sampling MOS switch, the one electrode being connected to said sampling capacitor and (ii) a gate electrode of said sampling MOS switch; and
a clamp capacitor connected to one of the source electrode and the drain electrode of said sampling MOS switch.
11. The sampling circuit according to claim 10 , further including:
a column-selecting MOS switch for turning on or off a connection between said sampling capacitor and an output line; and
a second damping capacitor connected to (i) one of a source electrode and a drain electrode of said column-selecting MOS switch, the one electrode being connected to said sampling capacitor and (ii) a gate electrode of said column-selecting MOS switch.