Compact low-noise active pixel sensor with progressive row reset
First Claim
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1. An active-pixel sensor including a radiation detector in a plurality of active pixel sensors organized into a sensor array, comprising:
- a transistor amplifier having an input and an output, wherein the input of the transistor amplifier is coupled to the radiation detector for generating an electrical signal output having a magnitude that is a function of the charge input generated by the radiation detector;
a switch coupled to the transistor amplifier for impressing the electrical signal from the transistor amplifier into an output line; and
a variable resistance coupled between the transistor amplifier and the radiation detector for resetting the charge input to the transistor amplifier to a predetermined signal level, the variable resistance and the transistor amplifier providing feedback to the charge input to the transistor amplifier during the resetting such that reset noise in the sensor is substantially nulled.
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Abstract
An imaging array of active pixel sensors uses a compact three transistor CMOS implementation for each pixel. A current source at the top of each column creates a distributed feedback amplifier for each pixel in a selected row. The reset amplifier acts as a variable resistance in the source-follower amplifier feedback circuit. The variable resistance is controlled by a range reset voltage applied to the reset amplifier thereby nulling the photodiode reset noise.
94 Citations
24 Claims
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1. An active-pixel sensor including a radiation detector in a plurality of active pixel sensors organized into a sensor array, comprising:
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a transistor amplifier having an input and an output, wherein the input of the transistor amplifier is coupled to the radiation detector for generating an electrical signal output having a magnitude that is a function of the charge input generated by the radiation detector;
a switch coupled to the transistor amplifier for impressing the electrical signal from the transistor amplifier into an output line; and
a variable resistance coupled between the transistor amplifier and the radiation detector for resetting the charge input to the transistor amplifier to a predetermined signal level, the variable resistance and the transistor amplifier providing feedback to the charge input to the transistor amplifier during the resetting such that reset noise in the sensor is substantially nulled. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An active-pixel sensor including a radiation detector in a two-dimensional array of active-pixel sensors organized into rows and columns of sensors, comprising:
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a transistor amplifier having an input and an output, wherein the input of the transistor amplifier is coupled to the radiation detector for generating an electrical signal output having a magnitude that is a format of the charge at the input of the transistor amplifier generated by the radiation detector;
a switch coupled to the transistor amplifier for impressing the electrical signal of the output of the transistor amplifier onto a column output line; and
a variable resistance coupled between the transistor amplifier and the radiation detector for resetting the charge at the input of the transistor amplifier to a predetermined signal level, the variable resistance and the transistor amplifier providing feedback to the charge input to the transistor amplifier during the resetting such that reset noise in the sensor is substantially nulled. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
a voltage source VSRC;
a current source ISRC; and
means for connecting the voltage source VSRC to the column output line during reset of the sensor and connecting the current source ISRC to the column output line during readout of the sensor.
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16. The active-pixel sensor of claim 14 further comprising an access supply coupled to a row output line of a two-dimensional array of active-pixel sensors organized into rows and columns of sensors.
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17. The active-pixel sensor of claim 16 wherein the access supply includes:
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a supply voltage Vdd;
a supply current Ibias; and
means for connecting the supply current Ibias to the row output line during reset of the sensors and connecting the supply voltage Vdd to the row output line during readout of the sensors.
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18. The active-pixel sensor of claim 16 wherein the access supply includes:
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a supply voltage Vdd;
a supply current Ibias; and
means for connecting the supply current Ibias to the row output line during reset of the sensors and connecting the supply voltage Vdd to the row output line during the readout of the sensors.
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19. The active-pixel sensor of claim 13 further comprising an access supply coupled to a row output line of a two-dimensional array of active-pixel sensors organized into rows and columns of sensors.
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20. The active-pixel sensor of claim 19 wherein the access supply includes:
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a supply voltage Vdd;
a supply current Ibias; and
means for connecting the supply current Ibias to the row output line during reset of the sensors and connecting the supply voltage Vdd to the row output line during readout of the sensors.
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21. A method for sensing an active pixel in a sensor array, comprising the steps of:
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generating an electrical signal output of a transistor amplifier and a radiation detector, wherein said electrical signal output has a magnitude that is a function of the charge input generated by the radiation detector;
impressing said electrical signal output from said transistor amplifier into an output line; and
resetting the charge input to said transistor amplifier to a predetermined level via a variable resistance coupled in parallel to a feedback capacitance of the transistor amplifier while substantially suppressing reset noise. - View Dependent Claims (22)
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23. An active pixel sensor including a radiation detector in a plurality of active pixel sensors organized into a sensor array, comprising:
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a transistor amplifier having a feedback capacitance, an input and an output, wherein the input of the transistor amplifier is coupled to the radiation detector for generating an electrical signal output having a magnitude that is a function of the charge input generated by the radiation detector;
a switch coupled to the transistor amplifier for impressing the electrical signal from the transistor amplifier into an output line; and
a variable resistance coupled in parallel with the feedback capacitance of the transistor amplifier such that both the variable resistance and the feedback capacitance are coupled in series to the radiation detector for resetting the charge input to the transistor amplifier to a predetermined signal level while substantially suppressing reset noise. - View Dependent Claims (24)
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Specification