Image sensor device and operation method thereof
Disclosed is an image sensor device which includes a pixel that outputs a first pixel signal to a first column line during a first time period and outputs a second pixel signal to the first column line during a second time period, and a clamp circuit that outputs a first clamp signal to the first column line during the first time period. During the first time period, a voltage of the first column line is determined based on the first pixel signal and the first clamp signal. The pixel operates based on a first power supply voltage, and the clamp circuit operates based on a second power supply voltage lower than the first power supply voltage.
1 . An image sensor device comprising:
a pixel configured to operate based on a first power supply voltage, output a first pixel signal to a first column line during a first time period and to output a second pixel signal to the first column line during a second time period;
a clamp circuit configured to operate based on a second power supply voltage that is lower than the first power supply voltage and to output a first clamp signal to the first column line during the first time period; and
a voltage regulator configured to generate the second power supply voltage based on the first power supply voltage,
wherein, during the first time period, a voltage of the first column line is determined based on the first pixel signal and the first clamp signal,
wherein the clamp circuit includes:
a clamp transistor connected between the second power supply voltage and a first node; and
a clamp select transistor connected between the first node and the first column line,
wherein the clamp transistor is configured to operate in response to a clamp control signal,
wherein the clamp transistor is turned on during the first time period,
wherein during the first time period, a voltage of the clamp control signal is higher than the second power supply voltage, and
wherein, during the first time period, a reset sampling operation is performed based on a voltage of the first column line.
2 . The image sensor device of claim 1 , wherein the clamp select transistor is configured to operate in response to a clamp selection signal.
3 . The image sensor device of claim 2 , further comprising:
a bias circuit,
wherein the bias circuit includes:
a bias amplifier including a first input terminal, a second input terminal, and an output terminal, wherein the bias amplifier is configured to output the clamp control signal through the output terminal based on a bias signal received through the first input terminal and a voltage of the second input terminal;
a bias transistor connected between the second power supply voltage and the second input terminal, wherein the bias transistor is configured to operate in response to the clamp control signal; and
a bias current source connected between the second input terminal and a ground node.
4 . The image sensor device of claim 3 , wherein the bias amplifier is configured to operate based on the first power supply voltage.
5 . The image sensor device of claim 3 , wherein the bias amplifier is configured to operate based on a third power supply voltage,
wherein the third power supply voltage is higher than the first power supply voltage, and
wherein the voltage of the clamp control signal is higher than the first power supply voltage.
6 . The image sensor device of claim 2 , wherein, during the first time period, the clamp transistor is configured to operate in a linear region.
7 . The image sensor device of claim 2 , wherein, in response to the clamp selection signal, the clamp select transistor is turned on in the first time period and is turned off in the second time period.
8 . An image sensor device comprising:
a control circuit configured to output a first control signal and a clamp selection signal;
a row decoder configured to output a reset signal, a transfer signal, and a selection signal based on the first control signal;
a pixel configured to operate based on a first power supply voltage, to operate in response to the reset signal, the transfer signal, and the selection signal such that a first pixel signal is output to a first column line during a first time period and a second pixel signal is output to the first column line during a second time period; and
a clamp circuit configured to operate based on a second power supply voltage that is lower than the first power supply voltage and to output a first clamp signal to the first column line during the first time period; and
a voltage regulator configured to generate the second power supply voltage based on the first power supply voltage,
wherein the pixel includes:
a photodiode configured to integrate charges in response to a light signal;
a transfer transistor connected between the photodiode and a floating diffusion node, and configured to operate in response to the transfer signal;
a reset transistor connected between a first power supply voltage and the floating diffusion node, and configured to operate in response to the reset signal;
a drive transistor connected between the first power supply voltage and a 0-th node, and configured to operate in response to a voltage of the floating diffusion node; and
a select transistor connected between the 0-th node and the first column line, and configured to operate in response to the selection signal,
wherein the clamp circuit includes:
a clamp transistor connected between a second power supply voltage and a first node, and configured to operate in response to a clamp control signal; and
a clamp select transistor connected between the first node and the first column line, and configured to operate in response to the clamp selection signal,
wherein the clamp transistor is turned on during the first time period,
wherein during the first time period, a voltage of the clamp control signal is higher than the second power supply voltage, and
wherein, during the first time period, a reset sampling operation is performed based on a voltage of the first column line.
9 . The image sensor device of claim 8 , wherein the control circuit is further configured to output a bias signal, and
wherein the image sensor device further comprises:
a bias circuit,
wherein the bias circuit includes:
a bias amplifier including a first input terminal, a second input terminal, and an output terminal, wherein the bias amplifier is configured to output the clamp control signal through the output terminal based on the bias signal received through the first input terminal and a voltage of the second input terminal;
a bias transistor connected between the second power supply voltage and the second input terminal, wherein the bias transistor is configured to operate in response to the clamp control signal; and
a bias current source connected between the second input terminal and a ground node.
10 . The image sensor device of claim 9 , wherein the bias amplifier is configured to operate based on the first power supply voltage.
11 . The image sensor device of claim 8 , wherein, during the first time period, the clamp transistor is configured to operate in a linear region.