CN1368825A

CN1368825A - Active pixel sensor with separation of resetting transistor with voltage source of other circuits

Info

Publication number: CN1368825A
Application number: CN 01102349
Authority: CN
Inventors: 杨孟璋; 庄朝贵
Original assignee: Sunplus Technology Co Ltd
Current assignee: Sunplus Technology Co Ltd
Priority date: 2001-02-05
Filing date: 2001-02-05
Publication date: 2002-09-11
Anticipated expiration: 2021-02-05
Also published as: CN1140991C

Abstract

An active picture element sensor contains the first voltage source to the charged to a photo unit as the reinitialize transistor switched on and the second voltage source to be supply to the transistors of series sources follower, read-out, switch and bias. The switch of source follower transistor is connected to the connecting point between reinitialized transistor and photodiode. The bias transistor schedules a bias for source follower transistor to read out photo signal at the connecting point when switch transistor is on. The above memtioned 1,2 voltage sources are different.

Description

The active picture-element sensor that reset transistor is separated with other circuit voltage sources

The present invention is the relevant initiatively technical field of picture-element sensor, refers to a kind of active picture-element sensor that reset transistor is separated with other circuit voltage sources especially.

Fig. 4 is the Organization Chart of the active image sensor of the golden oxygen of single pixel tradition half complementary processing procedure, pixel 41 (Pixel) is wherein powered by a power supply VCC, and its mode of operation is to drive reset signal (RESET) earlier to reset this pixel 41, after through one period time for exposure, drive column signal (ROW), to read the magnitude of voltage of representing photosignal, so that this magnitude of voltage of reading for the first time is stored in a correlated double sample circuit 42 (correlated-double-sampling from pixel output (Pixel Out); CDS) in.Afterwards, the pixel 41 of resetting again, and reset voltage is deposited in this correlated double sample circuit 42.Twice read-out voltage value subtracted each other, can obtain the potential difference that pixel 41 irradiations are produced, by this, can eliminate because transistor not the matching on processing procedure of pixel 41 caused fixed mode noise (the fixed pattem noise of critical voltage difference; FPN).

The active image sensor of aforementioned conventional gold oxygen half complementary processing procedure is to use single voltage source V CC, and be connected on the ceiling voltage of wafer, in order to obtain maximum exposure area, usually on layout, use same signal line, cause the noise between transistor to interfere with each other, and transistorized voltage is limited in maximum voltage value.Therefore, this kind design has the noise of following two aspects:

1. the random noise on the external voltage source, the source of this random noise is because the signal that voltage generator produced not is clean no noise, add the influence that is subjected to hot noise on the circuit (thermal nouse), make the voltage source that is fed on the pixel that sizable noise be arranged.

2. transistor turns or institute's voltage source pressure drop that causes and switch noise when switching.

More than two kinds of noises all with the change of work time point, even therefore there is CDS to handle, still can not eliminate this two kinds of noises in the circuit rear end.Therefore, aforementioned known active image sensor gives improved necessity in fact.

Creator whence is because of in this, and this is in the spirit of positive innovation, urgently thinks a kind of " active picture-element sensor that reset transistor is separated with other circuit voltage sources " that can address the above problem, and several times research experiment is eventually to the creation of finishing this novel progress.

The objective of the invention is is providing a kind of active picture-element sensor that reset transistor is separated with other circuit voltage sources, can reduce the noise that switch switches, and strengthen the elasticity of change in voltage, make two voltage sources can be under different considering its voltage swing of each self-adjusting.

For reaching aforesaid purpose, active picture-element sensor of the present invention comprises: first voltage source and second voltage source; One reset transistor is to be connected in this first voltage source; One photoelectric cell is to be connected in this reset transistor, with when this reset transistor is opened, by this first voltage source charging; And, source follower transistor, sense switch transistor and the bias transistor of serial connection, be by this second voltage fed, the gate of this source follower transistor is connected in the connected node between reset transistor and photodiode cell, this bias transistor is to set up a predetermined bias voltage for this source follower transistor, with when this sense switch transistor is opened, read the photosignal at connected node place; Wherein, this first voltage source and second voltage source are to be different voltage sources.

Because the present invention constructs novelty, can provide on the industry and utilize, and truly have the enhancement effect, so apply for a patent in accordance with the law.

For making your juror can further understand structure of the present invention, feature and purpose thereof, the attached now detailed description with graphic and preferred embodiment as after, wherein:

Fig. 1 is the circuit diagram that shows the active picture-element sensor that reset transistor is separated with other circuit voltage sources of the present invention.

Fig. 2 is a preferable layout that shows the active picture-element sensor that reset transistor is separated with other circuit voltage sources of the present invention.

Fig. 3 is another the preferable layout that shows the active picture-element sensor that reset transistor is separated with other circuit voltage sources of the present invention.

Fig. 4 is the Organization Chart for the active image sensor of the golden oxygen of single pixel tradition half complementary processing procedure.

Preferred embodiment about the active picture-element sensor that reset transistor is separated with other circuit voltage sources of the present invention, please be earlier with reference to circuit diagram shown in Figure 1, its comprise two different voltage source V RT1 and VRT2, one for example be the photoelectric cell of photodiode PD, a reset transistor M1, source follower transistor M2, a sense switch transistor M3 and a bias transistor M4, aforesaid transistor are metal-oxide-semiconductor (MOS) (MOS) transistor.The pixel output 12 of this active picture-element sensor (Pixel Out) is to be connected to a correlated double sample circuit 11, this correlated double sample circuit 11 by transistor M5 and M6, capacitor C R and CS, and subtraction circuit CIR formed, wherein, transistor M5 and M6 connect capacitor C R and CS separately, to control the charging to capacitor C R and CS respectively, capacitor C R and CS then are connected to two inputs of the subtraction circuit C1R that is made of differential amplifier respectively.

Aforementioned electric potential source VRT1 is the control via reset transistor M1, with when reset transistor M1 opens, the photodiode PD that is connected in reset transistor M1 is charged.

Aforementioned electric potential source VRT2 is transistor M2, M3 and the required voltage of M4 of supply serial connection, the gate of this source follower transistor M2 is connected in the connected node (netl) between reset transistor M1 and photodiode PD, this sense switch transistor M3 is that the column signal (ROW) by gate is controlled to be and opens or close, pole tension VLN maintains fixed voltage value between this bias transistor M4, with when sense switch transistor M3 opens, can be source follower transistor M2 and set up a suitable bias voltage.

In when operation, is to drive reset signal (RESET) earlier with reset transistor M1 conducting with aforesaid circuit, and replacement photodiode PD powers on and closes transistor M1 after being depressed into node (netl) voltage vcc.Cause node (netl) voltage to descend owing to produce photoelectric current behind the photodiode PD irradiation, after one period time for exposure, arrive the maximum photovoltage front opening sense switch transistor M3 that can record at node (netl) voltage, to read photosignal.

And aforementioned lights voltage exports this correlated double sample circuit 11 through source follower transistor M2 to by the output between transistor M3 and M4 12, and this moment, transistor M6 opened, and the photosignal value is deposited among the capacitor C S.Then, close sense switch transistor M3, and the photodiode PD voltage of resetting again is to Vcc, turn-on transistor M3 and M5 deposit reset voltage among the capacitor C R in.Again twice read-out voltage value subtracted each other through subtraction circuit CIR, can obtain the potential difference that photodiode PD irradiation is produced, wherein other voltage source V RT2 separates on the voltage source V RT1 that connect of photodiode PD and the pixel, and both must not be the maximum voltage sources in the wafer, and in operating process, can change VRT2 voltage and not influence optical diode PD glazing value of electrical signals according to actual needs, and can mat change VRT1 and VRT2 magnitude of voltage respectively to obtain the circuitry needed characteristic.

By aforementioned sensor circuit of the present invention, because it separates the employed voltage source V RT2 of other circuit on the employed voltage source V RT1 of photodiode PD and the pixel, therefore the voltage noise that is connect on can individual processing photodiode PD, because voltage VRT1 is the reset voltage of supply light electric diode PD only, so it is less and be easy to handle that the switch on it switches noise, and the unlikely direct reset voltage that influences photodiode PD of the reading circuit on the pixel and the change in voltage of source follower, therefore can obtain one on light two electrode tubes more is not subjected to the noise interference signals.In addition, this two voltage source V RT1 and VRT2 divided open supply, can strengthen the elasticity of change in voltage, make two voltage source V RT1 and VRT2 can be under different considering its voltage swing of each self-adjusting.

A kind of preferable layout of aforementioned circuit is as shown in Figure 2, it is to use two-layer stacked metal wire 21 and 22 to connect voltage source V RT1 and VRT2 respectively, to use metal wire difference supply light electric diode and other circuit required voltages of two different voltage sources, except that the interference that can exempt noise, can also save a part of space in pixel layout figure.Fig. 3 then shows second kind of preferable layout, and it is to use the two-layer metal wire of vertically putting 31 and 32 to connect voltage source V RT1 and VRT2 respectively, can further reduce because the metal wire parasitic capacitance causes the phenomenon that interferes with each other.

To sum up institute is old, and no matter the present invention is all showing it totally different in the feature of known techniques with regard to purpose, means and effect, for the quantum jump that the active picture-element sensor is made, earnestly asks your juror to perceive, and grants quasi patent early, so that Jiahui society, the true feeling moral just.Only it should be noted that above-mentioned many embodiment give an example for convenience of explanation, the interest field that the present invention advocated should be as the criterion so that claim is described certainly, but not only limits to the foregoing description.

Claims

1. the active picture-element sensor that reset transistor is separated with other circuit voltage sources is characterized in that, mainly comprises:

First voltage source and second voltage source;

One reset transistor is to be connected in this first voltage source:

One photoelectric cell is to be connected in this reset transistor, with when this reset transistor is opened, by this first voltage source charging; And

Source follower transistor, sense switch transistor and the bias transistor of serial connection, be by this second voltage fed, the gate of this source follower transistor is connected in the connected node between reset transistor and photodiode cell, this bias transistor is to set up a predetermined bias voltage for this source follower transistor, with when this sense switch transistor is opened, read the photosignal at connected node place;

Wherein, this first voltage source and second voltage source are to be different voltage sources.

2. the active picture-element sensor that reset transistor is separated with other circuit voltage sources according to claim 1, it is characterized in that, wherein this first and second voltage source is to connect two-layer stacked metal wire respectively to supply the pixel required voltage, so that exempt the interference of noise and save the pixel layout space.

3. the active picture-element sensor that reset transistor is separated with other circuit voltage sources according to claim 1, it is characterized in that, wherein this first and second voltage source is to connect the two-layer metal wire of vertically putting respectively to supply the pixel required voltage, so that reduce interfering with each other that the metal wire parasitic capacitance caused.

4. the active picture-element sensor that reset transistor is separated with other circuit voltage sources according to claim 1 is characterized in that, wherein this first and second voltage source can be adjusted change when the active picture-element sensor is operated.

5. the active picture-element sensor that reset transistor is separated with other circuit voltage sources according to claim 4 is characterized in that its pixel output is to be connected to a correlated double sample circuit.