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US 8,569,673 B2Granted
Image sensor with voltage-limiting device
AssigneeSTMicroelectronics (Grenoble 2) SAS
InventorLaurent Simony
Life of this patent
Estimating the term…
Abstract
An image sensor includes an active pixel, an amplifier stage, and a voltage-limiting stage. The active pixel is configured to generate an information signal. The amplifier stage is coupled to the active pixel and configured to amplify the information signal. The voltage-limiting stage is coupled to the amplifier stage and includes a current shunting device and a gain device. The current shunting device has a first terminal connected to an output of the amplifier stage, a second terminal connected to a reference voltage node, and a control terminal. The gain device is connected to the control terminal of the current shunting device and configured to decrease the voltage span required to cause the current shunting device to enter into a current shunting mode.
Claims25
An image sensor, comprising:
- a matrix of active pixels having several columns for delivering at least one information signal of an active pixel;
- and
- a processor coupled to receive the at least one information signal delivered by said active pixel, the processor including:
- at least one amplification stage biased by a current source, and
- a device for voltage-limiting the signal delivered on an output terminal of said at least one amplification stage, the device including an input terminal connected to the output terminal, a first transistor connected between the input terminal and a reference terminal connected to a reference power supply source, a gain device having an input connected to the input terminal, and an output connected to the gate of the first transistor, the gain device being configured so as to decrease the voltage span necessary to cause the first transistor to toggle from its off state to a state in which it absorbs the current provided by said current source,
- wherein the gain device comprises:
- a second transistor connected between a supply voltage of said current source and the gate of the first transistor, and having a gate connected to the input terminal, and
- a second current source connected to the drain of the second transistor.
5 more elements
An image sensor, comprising:
- a matrix of active pixels having several columns for delivering at least one information signal of an active pixel;
- a processor coupled to receive the at least one information signal delivered by said active pixel, the processor including:
- at least one amplification stage biased by a current source,
- a device for voltage-limiting the signal delivered on an output terminal of said at least one amplification stage, the device including an input terminal connected to the output terminal, a first transistor connected between the input terminal and a reference terminal connected to a reference power supply source, a gain device having an input connected to the input terminal, and an output connected to the gate of the first transistor, the gain device being configured so as to decrease the voltage span necessary to cause the first transistor to toggle from its off state to a state in which it absorbs the current provided by said current source;
- and
- at least one second amplification stage connected to said at least one amplification stage, the voltage-limiting device being connected between said amplification stage and second amplification stage.
3 more elements
An image sensor comprising:
- an active pixel configured to generate an information signal;
- an amplifier stage coupled to the active pixel and configured to amplify the information signal;
- and
- a voltage-limiting stage coupled to the amplifier stage and including:
- a current shunting device having a first terminal connected to an output of the amplifier stage, a second terminal connected to a reference voltage node, and a control terminal,
- a gain device connected to the control terminal of the current shunting device and configured to decrease the voltage span required to cause the current shunting device to enter into a current shunting mode, and
- a second current source connected between the control terminal of the current shunting device and ground.
4 more elements
An image sensor comprising:
- an active pixel configured to generate an information signal;
- an amplifier stage coupled to the active pixel and configured to amplify the information signal;
- and
- a voltage-limiting stage coupled to the amplifier stage and including:
- a current shunting device having a first terminal connected to an output of the amplifier stage, a second terminal connected to a reference voltage node, and a control terminal,
- a gain device connected to the control terminal of the current shunting device and configured to decrease the voltage span required to cause the current shunting device to enter into a current shunting mode,
- wherein the current shunting device is a first transistor, and
- wherein the gain device comprises a third and a fourth transistor connected in series, said third and fourth transistors being connected between the control terminal of the first transistor and a supply voltage of a current source, the gate of the third transistor being connected to an output of the amplifier stage, and an activation circuit connected to the gate of the fourth transistor and configured so as to control its state.
5 more elements
An image sensor comprising:
- an active pixel configured to generate an information signal;
- an amplifier stage coupled to the active pixel and configured to amplify the information signal;
- a voltage-limiting stage coupled to the amplifier stage and including:
- a current shunting device having a first terminal connected to an output of the amplifier stage, a second terminal connected to a reference voltage node, and a control terminal,
- a gain device connected to the control terminal of the current shunting device and configured to decrease the voltage span required to cause the current shunting device to enter into a current shunting mode;
- and
- a second amplifier stage connected to said amplifier stage, the voltage-limiting stage being connected between said amplifier stage and second amplifier stage.
4 more elements
An image sensor comprising:
- an active pixel configured to generate an information signal;
- an amplifier stage coupled to the active pixel and configured to amplify the information signal;
- and
- a voltage-limiting stage coupled to the amplifier stage and including:
- a current shunting device having a first terminal connected to an output of the amplifier stage, a second terminal connected to a reference voltage node, and a control terminal,
- a gain device connected to the control terminal of the current shunting device and configured to decrease the voltage span required to cause the current shunting device to enter into a current shunting mode,
- wherein the amplifier stage comprises a current source series connected with a second transistor, and
- wherein the voltage-limiting stage provides at least one limiting threshold whose value is dependent on characteristics of the second transistor.
5 more elements
Dependencies are inferred from the claim text.