JPH08251489A - Solid-state image pickup device - Google Patents

Abstract

PURPOSE: To obtain a video signal from which noise is eliminated quickly by subtracting a current corresponding to a dark voltage signal from a sum stored in a storage circuit comprising a current corresponding to an optical input, a current corresponding to a dark signal and an offset current specific to a voltage current converter. CONSTITUTION: A drive pulse ϕTG1 is set to a low level, a charge in response to an incident light generated in a photo diode PD is transferred to a gate of an amplifier transistor(TR) QA, a synthesis voltage signal (VD+VS) is fed to gate electrodes of MOSFETs QR1 , QR2 , from which an optical dark synthesis current signal (ID+IS+Ioff ) is outputted, where VD is a dark voltage, VS is a video voltage, ID is a dark current, IS is a video current and Ioff is an offset current specific to the converter. When a horizontal scanning circuit 7 provides sequentially drive pulses ϕH1, ϕH2 to horizontal read switch MOSFETs QB1 , QB2 and horizontal read switch M0SFETOH11 , OH12 , which are scanned sequentially, then only the video current IS after subtraction is outputted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state image pickup device.

[0002]

2. Description of the Related Art FIG. 7 is a schematic circuit diagram showing a schematic configuration of a conventional general solid-state image pickup device (including an amplification type solid-state image pickup device). In the solid-state imaging device shown in FIG.
An example is shown in which two pixels are arranged in a matrix of 2 rows and 2 columns, and here, a MOS including a photoelectric conversion unit is provided.
Type static induction transistor (MOSSIT (hereinafter, simply referred to as “SIT transistor”)) S ₁₁ , S ₁₂ ,
Using S _21, S _22, and using the signal reading method by the source follower.

Each SIT transistor S ₁₁ , S ₁₂ , S ₂₁ ,
The source of S ₂₂ is commonly connected to the vertical source lines (vertical read lines) 2a and 2b in each column of the matrix arrangement, and the drain is commonly connected to the power supply voltage VDS. In addition, each SIT transistor S ₁₁ , S ₁₂ ,
The gate electrodes of S ₂₁ and S ₂₂ are clock lines 13 scanned by the vertical scanning circuit 6 for each row of the matrix arrangement.
They are commonly connected to a and 13b, and are operated in row units by voltage drive pulses φG1 and φG2 sent from the vertical scanning circuit 6.

The vertical source lines 2a and 2b, on the other hand, are provided with optical signal output accumulation via optical signal output transfer MOS transistors TS ₁ and TS ₂ and dark output transfer MOS transistors TD ₁ and TD ₂ for each column. Capacitor C
S ₁ , CS ₂ and dark output storage capacitors CD ₁ , CD
_It is connected to ₂ and these storage capacitors (CS
₁ , CS ₂ , CD ₁ , CD ₂ ) are M for horizontal read selection
It is connected to the signal output line (horizontal read line) 16a and the dark output line (horizontal read line) 16b through the OS transistors TH _S1 , TH _S2 , TH _D1 and TH _D2 .

Generally, the signal output line 16a and the dark output line 16b have parasitic capacitances C _HS and C _HD .
Further, buffer amplifiers 17a and 17b are connected to one of the signal output line 16a and the dark output line 16b.

Further, on the other side of the signal output line 16a and the dark output line 16b, horizontal read reset MOS transistors TR _HS and TR for resetting the remaining video signal.
The drain of _HD is connected, and the drive pulse generating circuit 1 is connected to the gate electrodes of the horizontal read reset MOS transistors TR _HS and TR _HD via the clock line 18a.
When the drive pulse φRSH sent from the circuit 8 is supplied, the horizontal read reset MOS transistor TR
_HS and TR _HD are working.

The gate electrodes of the horizontal read selection MOS transistors TH _S1 and TH _D1 are connected to the horizontal selection signal line 7a of the horizontal drive circuit 7, and the horizontal read selection MOS is also used.
The gate electrodes of the transistors TH _S2 and TH _D2 are commonly connected to the horizontal selection signal line 7b of the horizontal drive circuit 7, and drive pulses φH1 and
Horizontal reading is controlled by φH2.

The drive pulse φTS sent from the drive pulse generation circuit 14 through the optical signal clock line 14a is applied to each gate electrode of the optical signal output transfer MOS transistors TS ₁ and TS _{2 and} the dark output transfer. The drive pulse φTD sent from the drive pulse generation circuit 15 is supplied to the respective gate electrodes of the power MOS transistors TD ₁ and TD ₂ through the dark output clock line 15a. , ΦTD, the optical signal output transfer MOS transistors TS ₁ and TS ₂ and the dark output transfer MOS transistors TD ₁ and TD ₂ are alternately operated in a predetermined order.

On the other hand, the vertical source lines 2a and 2b are provided with reset MOS transistors T for each column.
The reset MOS transistors T are connected to the drains of R _V1 and TR _V2 and the constant current sources 12a and 12b.
The sources of R _V1 and TR _V2 are grounded, and each constant current source 12a,
The power supply voltage VC is supplied to 12b.

Incidentally, the reset MOS transistor T
The gate electrodes of R _V1 and TR _V2 are connected to the drive pulse generation circuit 11 via the clock line 11 a, and the drive pulse φRSV sent from the drive pulse generation circuit 11
Of the reset MOS transistors TR _V1 and TR _V2
When supplied to the gate electrode of, the reset MOS transistors TR _V1 and TR _V2 operate to operate the vertical source lines 2a and 2b and the optical signal output storage capacitor CS.
₁ , CS ₂ and dark output storage capacitors CD ₁ , CD ₂
Is designed to be reset.

Next, the operation of the conventional solid-state image pickup device shown in FIG. 7 will be described with reference to the timing chart shown in FIG. First, as shown in FIG. 8, the drive pulse φTS is set to the high level in the period t ₁₁ . As a result, the drive pulse φRSV that is already at the high level
Like the reset MOS transistors TR _V1 and TR _V2 that are made conductive by the optical signal output transfer MO
The S transistors TS ₁ and TS ₂ are also rendered conductive.

As a result, the reset MOS transistors TR _V1 and TR _V2 and the optical signal output transfer MOS transistors TS ₁ and TS ₂ become conductive, and the signal charges remaining in the optical signal output storage capacitors CS ₁ and CS ₂ are removed. The light is discharged from the sources of the reset MOS transistors TR _V1 and TR _V2 through the vertical source lines 2a and 2b, and the optical signal output storage capacitors CS ₁ and CS ₂ are reset (initialized) to the ground level. At this time, the gates of the SIT transistors S ₁₁ , S ₁₂ , S ₂₁ , and S ₂₂ are in a state where the charges photoelectrically converted by the photoelectric conversion unit are accumulated.

Next, in the period t ₁₂ , the drive pulse φRS
Set V to low level and reset MOS transistor T
_Turn off R _V1 and TR _V2 , and drive pulse φ
The first line of the SIT and the voltage of the G1 to read level VG ₂
The transistors S ₁₁ and S ₁₂ are set to the read state.

As a result, the SIT transistors S ₁₁ and S _{12 are}
Performs the source follower operation, and the SIT transistor S
_The charge accumulated in the gates of ₁₁ and S ₁₂ is read out to the vertical source lines 2a and 2b, and at the same time, the optical signal output transfer MOS transistors TS ₁ and TS ₂ which are in a conductive state by the driving pulse φTS which is already at the high level. The electric charge (video signal) is stored in the optical signal output storage capacitors CS ₁ and CS ₂ via the. It should be noted that this video signal includes a component that is a combination of the dark component (D) and the optical signal component (S), and this video signal is hereinafter referred to as a "composite voltage signal (VD + VS)".

Next, in the period t ₁₃ , the drive pulse φTS
Is set to a low level to turn off the optical signal output transfer MOS transistors TS ₁ and TS ₂ . As a result, the combined voltage signal (VD + VS) remains held in the optical signal output storage capacitors CS ₁ and CS ₂ .

At this time (time period t ₁₃ ), the voltage of the drive pulse φG ₁ is set to the set level VG ₁ , and SI of the first row is set.
The read operation of the T transistors S ₁₁ and S ₁₂ is stopped.
Further, the drive pulse φRSV is set to the high level to bring the reset MOS transistors TR _V1 and TR _V2 into the conductive state. As a result, the vertical source lines 2a and 2b are grounded.

Next, in the period t ₁₄ , the driving pulse φG1
To the reset level VG ₃ . As a result, the reset M, which has already been set to the high level and is in the conductive state,
The OS transistors TR _V1 and TR _V2 reset (initialize) the SIT transistors S ₁₁ and S ₁₂ in the first row. The SIT transistors S ₁₁ and S of the first row are
_After the reset of ₁₂ , the voltage of the drive pulse φG1 is set to the set level VG ₁ , and the operations of the SIT transistors S ₁₁ and S ₁₂ of the first row are stopped.

Next, in the period t ₁₅ , the drive pulse φTD
Is set to a high level to bring the dark output transfer MOS transistors TD ₁ and TD ₂ into a conductive state. As a result, the reset MOS, which has already become high level and is in the conductive state,
The transistors TR _V1 and TR _V2 are electrically connected to the dark output transfer MOS transistors TD ₁ and TD ₂ , and the signal charges remaining in the dark output storage capacitors CD ₁ and CD ₂ are reset MOS via the vertical source lines 2 a and 2 b. The dark output storage capacitors CD ₁ and CD ₂ are discharged from the sources of the transistors TR _V1 and TR _V2 , and are reset (initialized) to the ground level.

Next, in the period t ₁₆ , the drive pulse φRS
V is set to the low level, the reset MOS transistors TR _V1 and TR _V2 are cut off, and the voltage of the drive pulse φG1 is set to the read level VG ₂ to set the SI of the first row.
The T-transistors S ₁₁ and S ₁₂ are set to the read state.

As a result, the SIT transistors S ₁₁ and S _{12 are}
Performs the source follower operation, and the video signal after the reset of the SIT transistors S ₁₁ and S ₁₂ is read to the vertical source lines 2a and 2b, and the dark output which is in the conductive state by the driving pulse φTD which is already at the high level. Transfer M
The video signal is stored in the dark output storage capacitors CD ₁ and CD ₂ via the OS transistors TD ₁ and TD ₂ . It should be noted that this video signal includes only the dark component (D), and this video signal is hereinafter referred to as "dark voltage signal VD".

Next, at the end of the period t ₁₆ , the drive pulse φG1 is set to the set level VG ₁ , the drive pulse φTD is set to the low level, and the drive pulse φRSV is set to the high level. As a result, the SIT transistors S ₁₁ and S ₁₂ of the first row are again brought into a state of accumulating charges due to light incidence in the gate, and the dark output accumulating capacitors CD ₁ and CD ₂ are turned off, The dark voltage signal VD is held in the dark output storage capacitors CD ₁ and CD ₂ . Further, the reset MOS transistors TR _V1 and TR _V2 are rendered conductive.

Next, in the period t ₁₇ , first, the horizontal read circuit 6 selects the horizontal read selection MOS transistor T.
A drive pulse φH1 is applied to the gate electrodes of H _S1 and TH _D1 . As a result, the horizontal read selection MOS transistor T
H _S1 and TH _D1 operate, and the optical signal output storage capacitor C
The combined voltage signal (VD + VS) stored in S ₁ is read out on the signal output line 16a, and the dark voltage signal VD stored on the dark output storage capacitor CD ₁ is read out on the dark output line 16b, respectively, and the buffer amplifier 17a is read. And 17b to the output terminal VO.

In general, since the signal output line 16a and the dark output line 16b have parasitic capacitances C _HS and C _HD , the combined voltage signal (VD + VS) is applied to the signal output line 16a and the dark voltage signal VD. Is read out to the dark output line 16b, a part of each voltage signal ((VD + VS), VD) is held in the parasitic capacitances C _HS , C _HD , and the signal output line 1
6a and the dark output line 16b. Therefore, by applying the drive pulse φRSH to the horizontal read reset MOS transistors TR _HS and TR _HD , the voltage signal ((VD +
VS) and VD) are discharged, and the signal output line 16a and the dark output line 16b are reset (initialized) to the ground level.

Next, the horizontal drive circuit 6 applies a drive pulse φH2 to the gate electrodes of the horizontal read selection MOS transistors TH _S2 and TH _D2 again. As a result, the horizontal read selection MOS transistors TH _S2 and TH _D2 operate and the combined voltage signal (VD + VS) stored in the optical signal output storage capacitor CS ₂ is output to the signal output line 16a and the dark output storage capacitor CD. _The dark voltage signal VD stored in ₂ is read out to the dark output line 16b and output to the output terminal VO via the buffer amplifiers 17a and 17b.

Then, a driving pulse φRSH is applied to the horizontal read reset MOS transistors TR _HS and TR _HD to discharge the voltage signals ((VD + VS), VD) remaining on the signal output line 16a and the dark output line 16b. , Reset (initialize) the signal output line 16a and the dark output line 16b to the ground level.

As described above, during the period t ₁₇ , the drive pulses (φH1, φH2) and the drive pulse φRSH sent from the horizontal drive circuit 6 are sequentially set to the high level and the low level to make the horizontal read selection MOS. Transistor TH _S1 ,
TH _D1 , TH _S2 , and TH _D2 are operated, and the voltage signals ((VD +) stored in the optical signal output storage capacitors CS ₁ and CS ₂ and the dark output storage capacitors CD ₁ and CD ₂ are stored.
VS), VD) through the signal output line 16a, the dark output line 16b and the buffer amplifiers 17a, 17b to the output terminal VO
After that, the horizontal read reset MOS transistors TR _HS and TR _HD are operated to reset (initialize) the signal output line 16a and the dark output line 16b.

The output terminal VO and the buffer amplifier 17a
And 17b, a subtraction processing amplifier 17c is provided. This is because the composite voltage signal (VS + VD) is read out to the signal output line 16a and the dark voltage signal VD is read out to the dark output line 16b, so that subtraction processing ((VS + VD) -VD) is performed on these signals. , For extracting only the true video signal (optical voltage signal VS).

The above operation is similarly performed for the SIT transistors S ₂₁ , S ₂₂ of the second row (t ₂₁ ~
t ₂₇ ), so-called raster scan is performed.

In the solid-state image pickup device which performs the read operation by such a source follower, since the charge is amplified by the source follower amplifier and read, the S / N ratio is high, the linearity of the video signal is good, and the fixed pattern noise (FP
Pixels (SIT transistors S ₁₁ , S) that are the main cause of N)
_12, S _21, the threshold variation of S ₂₂₎ each is, dark voltage signal V
By storing D (CD ₁ , CD ₂ ), there is an advantage that it can be easily removed by taking a difference from the video signal composed of the composite voltage signal (VS + VD).

[0030]

However, in the conventional solid-state image pickup device described above, the transistors (S ₁₁ , S
₁₂ as a voltage charge amplified by, S _21, S _22),
Since the data was read out to the horizontal read lines (16a, 16b) as it is, the following problems occur.

First, there is a problem that it takes time to read the amplified charges (video signal). This is because the horizontal read lines have parasitic capacitances (C _HS , C _HD ).
When the video signal (composite voltage signal (VD + VS), dark voltage signal (VD)) is read out to the output line, the parasitic capacitance must be charged, and after that, the parasitic capacitance must be reset. , The read operation speed becomes slow.

Second, the combined voltage signal (VD + VS),
Two lines (two lines) of horizontal read lines (16a, 16b) are provided for outputting the dark voltage signal (VD) separately, and for this reason, a buffer amplifier (17a, 1) is provided.
Since two 7b) must be provided, not only becomes expensive, but also effective random noise becomes √2 times.

Thirdly, in the conventional solid-state image pickup device,
Parasitic capacitances (C _HS , C) are applied to the horizontal read lines (16a, 16b).
_HD ) exists, so that there is a problem that the voltage distribution of the video signals (the composite voltage signal (VD + VS) and the dark voltage signal VD) read out to the signal line is lowered by the charge distribution due to the parasitic capacitance.

Fourth, the buffer amplifiers (17a, 17b) provided in the conventional solid-state image pickup device are generally
In order to prevent the electric charge (video signal) accumulated in the capacitors (CS ₁ , CS ₂ , CD ₁ , CD ₂ ) from being attenuated,
The input impedance is designed to be high. That is, the buffer amplifier (17
In a and 17b), the input impedance is made high in order to improve the S / N ratio of the video signal.

However, if the performance of the buffer amplifier is set to a high impedance, the buffer amplifier is apt to receive induced noise from the outside, resulting in a problem that the S / N ratio of the video signal is apt to deteriorate.

The present invention has been made in view of the above problems, and an object of the present invention is to obtain a solid-state image pickup device capable of improving the S / N ratio of a video signal.

Another object of the present invention is to obtain a solid-state image pickup device in which a video signal read operation is fast.

Another object of the present invention is to obtain a solid-state image pickup device which is less susceptible to induction noise.

[0039]

In order to achieve the above-mentioned object, a solid-state image pickup device according to a first aspect of the present invention is arranged in a two-dimensional matrix, and converts charges according to incident light into a voltage signal. And a plurality of vertical read lines for sequentially scanning the pixels in the column direction in common for each row of the matrix array and extracting a voltage signal from each pixel for each column, And a horizontal read-out line for sequentially extracting the time-series voltage signals of each row by scanning the vertical read-out line in the row direction, and each vertical read-out line is connected to each. From the voltage signal consisting of the first component according to the sum of the incident light amount and the dark output, which are output from the pixel at different times when the scanned pixels are sequentially scanned for each row, and the second component according to the dark output. Current corresponding to each voltage signal And a sum of the offset current peculiar to the voltage-current converting means and the current signal corresponding to the voltage signal composed of the first component are provided on the output side of each voltage-current converting means. Of the first combined current signal corresponding to the current signal and the second combined current signal corresponding to the sum of the offset current specific to the voltage-current conversion means and the current signal corresponding to the voltage signal including the second component. A current storing means for storing is provided, and between the voltage / current converting means and the horizontal read line, the other one of the first combined current signal and the second combined current signal is already stored in the current storage means. The present invention is characterized in that switching means for respectively reading out a current signal consisting of a component corresponding to the amount of incident light by subtraction from the combined current signal present in the horizontal readout line is provided.

Further, in the solid-state imaging device according to the invention described in claim 2, in the solid-state imaging device according to claim 1,
The pixel has a photoelectric conversion element that generates and accumulates electric charges according to incident light, an amplification element that generates a voltage signal corresponding to the electric charges received in the control region, and an amplification element that accumulates charges generated and accumulated by the photoelectric conversion element. And a reset control element for selectively resetting charges in the control area of the amplification element.

[0041]

The solid-state image pickup device according to the first aspect of the invention is
It is mainly composed of a plurality of pixels, a plurality of vertical read lines, a horizontal read line, a voltage / current conversion means, a current storage means, and a switching means.

Here, the plurality of pixels are arranged in a two-dimensional matrix, and the charges corresponding to the incident light are converted into voltage signals and output. The plurality of vertical read lines sequentially scan the pixels in common in each row of the matrix array in the column direction to take out signal output from each pixel for each column. The horizontal read-out line scans the plurality of vertical read-out lines in the row direction to sequentially take out a time-series signal output for each row.

Further, the voltage-current converting means is provided in each of the plurality of vertical read lines, and has a voltage composed of a first component corresponding to the sum of the incident light amount and the dark output of the voltage signals output from the plurality of pixels. A current signal corresponding to each of the signal and the voltage signal including the second component corresponding to the dark output is output.

Further, the current storage means is provided on the output side of each voltage-current conversion means and responds to the sum of the offset current peculiar to the voltage-current conversion means and the current signal corresponding to the voltage signal composed of the first component. A second combined current signal, and a second current corresponding to a sum of an offset current peculiar to the voltage-current converting means and a current signal corresponding to the voltage signal including the second component.
Either one of the combined current signals is stored.

Further, each switching means is provided between each voltage / current converting means and the horizontal read line, and either one of the first combined current signal and the second combined current signal output from the voltage / current converting means. A current signal composed of a component corresponding to the amount of incident light by subtraction of the other and the combined current signal already stored in the current storage means is sequentially read out to the horizontal read line.

That is, in the present invention, a voltage signal consisting of the first component corresponding to the sum of the incident light quantity and the dark output first outputted from the plurality of pixels and a voltage signal consisting of the second component corresponding to the dark output. One of the two is converted into a current signal corresponding to the voltage signal by the voltage-current conversion means,
The converted current signal is stored in the current storage means.

Here, when the voltage signal is converted into the current signal by the voltage-current converting means, a unique offset current flowing through the voltage-current converting means itself may be superimposed on the converted current signal. Therefore, the current storage means eventually stores the combined current signal in which the current signal corresponding to the voltage signal and the offset current are combined.

Here, for convenience of the following description, assuming that the voltage signal initially output from the plurality of pixels is a voltage signal composed of the first component according to the sum of the incident light quantity and the dark output, in this case, The combined current signal stored in the current storage means is the first combined current signal.

After that, one of the voltage signal consisting of the first component corresponding to the sum of the incident light amount and the dark output and the voltage signal consisting of the second component corresponding to the dark output, which is subsequently output from the plurality of pixels, is the other. , That is, in this case, the second according to the dark output
The voltage signal composed of the components is converted by the voltage-current conversion means.
It is converted into a current signal corresponding to the voltage signal. At this time as well, it is conceivable that a unique offset current flowing through the voltage-current conversion means itself is superimposed on the converted current signal, and as a result, the voltage-current conversion means outputs a second component corresponding to the dark output. The second combined current signal obtained by combining the current signal corresponding to the voltage signal and the offset current is output.

Next, by operating the plurality of switching means, the first combined current signal stored in the storage means and the second combined current signal output from the voltage / current converting means are read out to the horizontal read line. However, at this time, the first combined current signal and the second combined current signal are combined so as to be subtracted from each other, whereby only the current signal composed of the component corresponding to only the amount of incident light is transmitted to the horizontal readout line. Read out.

That is, the first combined current signal is the current signal (IS +) corresponding to the voltage signal (VS + VD) consisting of the first component according to the sum of the incident light amount (S) and the dark output (D).
ID) and the offset current (I _off ) are current signals (IS + ID + I _off ), and the second combined current signal is a voltage signal (VD) including a second component corresponding to the dark output (D). ) And a current signal (ID +) corresponding to the offset current (I _off ).
I _off ).

Therefore, by the operation of each switching means, the first combined current signal-second combined current signal =
The subtraction of (IS + ID + I _off ) − (ID + I _off ) = IS is performed, and eventually only the current signal (IS) having a component corresponding to the incident light amount is read out to the horizontal read line.

Therefore, since the video signal read out to the horizontal read-out line is read out as a current signal, the charge distribution due to the parasitic capacitance existing in the horizontal read-out line is eliminated, and the S / N ratio of the video signal can be improved. With
It is possible to use an output circuit having a low input impedance for the horizontal read line, and the output video signal is not affected by inductive noise from the outside.

Further, in the present invention, since the video signal read to the horizontal read line is a current signal, the read operation of the video signal can be speeded up.

That is, in the conventional solid-state image pickup device,
Since the video signal read to the horizontal read line is read as a voltage, the parasitic capacitance of the horizontal read line cannot be ignored. For example, when the video signal is read to the horizontal read line, after charging the parasitic capacitance, The charge accumulated in the parasitic capacitance has to be reset, which causes a problem that the read operation speed becomes slow. However, in the present invention, the video signal read to the horizontal read line is converted into a current signal. Since the data is read out to the horizontal read line later, even if there is a parasitic capacitance, it is not necessary to charge or reset the parasitic capacitance, and the read operation of the video signal can be speeded up.

In the solid-state image pickup device according to a second aspect of the present invention, in the solid-state image pickup device according to the first aspect, the pixels include, for example, a photoelectric conversion element, an amplification element, a transfer control element, and a reset control element. Composed of.

Here, the photoelectric conversion element generates and accumulates electric charges according to incident light. The amplifying element produces a voltage signal according to the charge received in the control region. The transfer control element is
The charges generated and accumulated in the photoelectric conversion element are selectively transferred to the control region of the amplification element. The reset element selectively resets the charge in the control region of the amplification element.

That is, in the MOS type static induction transistor (MOSSIT) shown in the conventional example, the combined voltage signal (VD + VS) and the dark voltage signal (V
Since the pixel resetting (initializing) operation is performed during the output of D) and D, the reading operation of the video signal is delayed by the time of performing the resetting operation. However, in the pixel having the configuration according to claim 2, A voltage signal (video signal) consisting of a first component according to the sum of incident light quantity and dark output and a second signal according to dark output
While outputting the voltage signal (video signal) consisting of components,
Since both the signals can be output without performing the so-called pixel reset (initialization) operation, the video signal can be read at a higher speed.

[0059]

1 is a schematic circuit diagram showing a schematic configuration of a solid-state image pickup device according to an embodiment of the present invention. In the solid-state imaging device shown in FIG. 1, a case where four pixels 1 are arranged in a matrix of 2 rows and 2 columns is illustrated for the sake of description. Each pixel 1 includes a photodiode PD that generates and accumulates charges according to incident light, and an amplifying transistor that outputs a signal corresponding to the charges received in the control region as a voltage signal (N-channel type in this embodiment). JFET) QA, a transfer MOS transistor (P-channel type) QT that selectively transfers the charges generated and accumulated in the photodiode PD to the control region of the amplification transistor QA, and the control region of the amplification transistor QA. And a reset MOS transistor (P-channel type) QP for selectively initializing the electric charges of the
The signal is read by the source follower operation by.

The source of each amplifying transistor QA is commonly connected to the vertical source lines 2a and 2b for each column of the matrix arrangement, and each amplifying transistor QA is also connected.
The power supply voltage VDS is commonly applied to each pixel on the drain of A and the cathode side of the photodiode PD. The anode side of each photodiode PD and the gate (control area) of each amplification transistor QA are connected to the source / drain of the transfer MOS transistor QT.

The transfer gate electrode of the transfer MOS transistor QT has a vertical scanning circuit 6 for each row of the matrix arrangement.
When the drive pulse φTG1 or φTG2 sent from the vertical scanning circuit 6 is applied, the transfer MOS is commonly connected to the clock line 3a or 3b.
The transistors QT are operated sequentially for each row.

The drain of the reset MOS transistor QP is commonly connected to the clock line 5a or 5b connected to the vertical scanning circuit 6 for each row of the matrix arrangement, and the reset MOS transistor QP is also connected.
The gate electrode of is connected to the drive pulse generation circuit 4 in common for each pixel via the row line 4a. Further, the source of the reset MOS transistor QP is a transfer MO.
It is shared with the drain of the S transistor QT. When the drive pulse φRG sent from the drive pulse generating circuit 4 is applied to the gate electrode of the reset MOS transistor QP, the reset MOS transistor QP operates.

[0063] The vertical source lines 2a, 2b on the one hand, the voltage for each column - current conversion MOS transistors QR _1, is connected to the gate electrode of the QR _2, each voltage - current conversion MOS transistors QR ₁ , QR ₂ have their sources connected to a constant voltage source VS via resistors R ₁ or R ₂ , respectively. Further, the drains are isolation switch MOS transistors (N-channel type) QB ₁ , Q
A horizontal read switch MOS transistor (N channel type) QH ₁₁ , Q connected to the source of B ₂
And each through H ₁₂ and the MOS transistor (N-channel type) shunt QH _21, QH _22, the horizontal read lines 8a
And the bias line 8b.

It should be noted that the horizontal read line 8a and the bias line 8b have a current − whose input is virtually grounded to the constant power source VR.
A voltage converting / amplifying circuit 9 is provided. The video signal current read to the horizontal read line 8a is converted into a video signal voltage by the current-voltage conversion circuit 9 and then sequentially output from the output terminal VO.

The gate electrodes of the MOS transistors QB ₁ and QB ₂ for separation switches are clock lines 23a.
Are commonly connected to the drive pulse generating circuit 23 via the drive pulse generating circuit 23, and when the drive pulse φD sent from the drive pulse generating circuit 23 is applied, the MOS transistors QB ₁ and QB ₂ for separation switches operate (open and close). It has become.

The separation switch MOS transistors QB ₁ and QB ₂ are connected to the load side and to the voltage-current conversion M.
It is provided to separate (insulate) the OS transistors QR ₁ and QR ₂ .

The gate electrodes of the horizontal read switch MOS transistors QH ₁₁ and QH ₁₂ are connected to the horizontal selection signal lines 7a ₁ and 7a ₂ connected to the horizontal scanning circuit 7, respectively. Horizontal readout is controlled by the drive pulses φH1 and φH2 that are sent out.

The horizontal selection signal lines 7a ₁ and 7a
₂ includes the shunt MOS transistors QH ₂₁ and Q
Reversing inverter 21a connected to the gate electrode of the H _22,
21b is connected to the inverter 21 for inversion.
a and 21b are drive pulses φH from the horizontal scanning circuit 7.
When 1 and φH2 are not sent, the shunt M
A voltage is applied to the gate electrodes of the OS transistors QH ₂₁ and QH ₂₂ to generate the shunt MOS transistors QH ₂₁ and QH.
₂₂ is designed to work. That is, the horizontal read switch MOS transistors QH ₁₁ and QH ₁₂ and the shunt MOS transistors QH ₂₁ and QH ₂₂ operate complementarily.

[0069] Further, each of the voltage - drain current conversion MOS transistors QR _1, QR ₂ is a connection line 2
0a ₁ and 20b ₁ through M for voltage-current conversion
A current storage circuit (current storage means) 20 that stores and outputs the currents output from the OS transistors QR ₁ and QR _2.
a and 20b are connected.

The current storage circuits 20a and 20b are also provided.
Are commonly connected to the drive pulse generating circuit 22 via the clock line 22a, and when the drive pulse φD sent from the drive pulse generating circuit 22 is applied, each of the current storage circuits 20a and 20b operates. It has become.

Further, the vertical source lines 2a, 2b
On the other hand, is a reset switch MOS for each column.
The drains of the transistors (N-channel type) TR _V1 and TR _V2 are connected to the constant current sources 12a and 12b, the sources of the reset switch MOS transistors TR _V1 and TR _V2 are grounded, and the constant current sources 12a and 12b are connected. Is supplied with a power supply voltage VC (negative).

The gate electrodes of the reset switch MOS transistors TR _V1 and TR _V2 are connected to the drive pulse generation circuit 11 via the clock line 11 a, and the drive pulse generated from the drive pulse generation circuit 11 is connected to the drive pulse generation circuit 11. φRSV is the reset switch MOS transistor T
When applied to the gate electrodes of R _V1 and TR _V2, the reset switch MOS transistors TR _V1 and TR _V2 are operated.

Next, the operation of the solid-state imaging device shown in FIG. 1 will be described with reference to the pulse timing chart shown in FIG. In FIG. 2, the periods t _{10 to} t ₁₈ are
The readout operation of the pixel 1 in the first row is shown, and the period t
_{20 to} t ₂₈ show the read operation of the pixel 1 on the second row.

As shown in FIG. 2, in the period t ₁₀ ,
Since the drive pulses φTG1 and φTG2 are at the high level, each transfer MOS transistor QT is in the non-conductive state (OFF). Further, since the drive pulse φRG is at the low level, each reset MOS transistor QP is in the conductive state (ON). Further, since the drive pulse φRSV is at the high level, the reset switch MOS transistors TR _V1 and TR _V2
Is in a conductive state (on). Also, drive pulse φ
Since S is at the low level, the MOS transistors QB ₁ and QB ₂ for separation switch are in the non-conducting state (open state), and since the drive pulse φD is at the high level, the current storage circuits 20a and 20b are in the non-operating state ( Off).

Further, as shown in FIG. 2, in the period t ₁₀ , the drive pulses φRD1 and φRD2 are at the low level (the voltage level is the set level VRSG), and the drive pulse φRG is
Is set to a low level, the voltage (setting level VRSG) passes through the gates (control regions) of the reset MOS transistors QP that are in a conductive state.
It is transmitted to the gate (control region) of A, and the gate (control region) of these amplifying transistors QA is biased to the set level VRSG.

Further, during this period t ₁₀ , since the reset switch MOS transistors TR _V1 and TR _V2 are in the conductive state, the sources of the respective amplification transistors QA and the respective voltage-current conversion MOS transistors QR.
The gates (control regions) of ₁ and QR ₂ are grounded.
It should be noted that, during this period t ₁₀ , charges (signal charges) corresponding to incident light are generated and accumulated in each photodiode PD.

Next, in the period t ₁₁ , the drive pulse φRD
When 1 is set to the high level (the voltage level is the read level VRDG), the voltage (the read level) is passed through the gate (control region) of each reset MOS transistor QP of the first row which is already in the conductive state. VRDG) is transmitted to the gate (control area) of the amplification transistor QA of each pixel 1 in the first row, the amplification transistor QA in the first row is selected (turned on), and the amplification transistor QA
The gate (control region) of is biased to the read level VRDG. The amplification transistors QA in the second row are
Since the drive pulse φRD2 is at the low level (the voltage level is the set level VRSG), the gates (control areas) of the amplification transistors QA on the second row are biased to the set level VRSG and are not selected (OFF). It

Next, in the period t ₁₂ , the drive pulse φRG
Is set to a high level, the reset MOS transistor QP becomes non-conductive (OFF), and each amplification transistor QA in the first row is set in a floating state.
The gate (control area) of each amplifying transistor QA in the first row has the read level due to the effect of parasitic capacitance.
Holds biased to VRDG.

In this way, the gate (control area) of the amplification transistor QA is biased to the read level VRDG,
Even when the reset MOS transistor QP is turned off, the state in which the gate (control area) of the amplification transistor QA remains biased to the read level VRDG is generally called “reset (initialization)” of the pixel 1. However, when the reset MOS transistor QP is set to the non-conducting state, thermal noise of the reset MOS transistor QP is added as reset noise (so-called KTC noise) to the gate (control area) of the amplification transistor QA.

That is, when the gate (control area) of each amplifying transistor QA is reset, the gate voltage V _GD of each amplifying transistor QA is expressed by the following equation. V _GD = VRDG + VN ... However, VN = (KT / C) ^1/2 K: Boltzmann constant T: Absolute temperature C: Gate capacitance

Next, in the period t ₁₃ , the driving pulse φRS
When V is set to a low level and the reset switch MOS transistors TR _V1 and TR _V2 are turned off (OFF), each amplification transistor QA on the first row selected in the period t ₁₁ operates as a source follower. The potential V _SD of the source of these amplification transistors QA is
The current flowing between the drains (drain current) rises until it becomes IB (the current value flowing through the constant current sources 12a and 12b).

The source follower operation causes the source
The potential V _SD of the source of each amplification transistor QA when the current flowing between the drains becomes IB is expressed by the following equation. V _SD = V _GD −VT ... where V _GD is the gate voltage when the gate (control area) of each amplification transistor QA in the first row is biased to the read level VRDG (see the equation). VT: Gate when the drain current of each amplification transistor QA is IB
Source-to-source voltage.

Therefore, the above equation is further expressed as the following equation using the above equation. V _SD = V _GD -VT ... = VRDG + VN-VT ... (∵V _GD = VRDG + VN. See the formula.)

As a result, the source potential V _SD of each amplification transistor QA is applied to the vertical source lines 2a and 2b.
A voltage according to (Equation) is output as a voltage signal.
Then, the output voltage signal corresponds to each voltage-current conversion MOS transistor Q from which the residual charge has already been discharged.
It is sent to the gate electrodes of R ₁ and QR ₂ .

Generally, the gate-source voltage V
It is known that the value of T (equation or equation) varies for each voltage amplification transistor QA. Therefore, the voltage-current conversion MOS transistors QR ₁ , QR ₂
Since the voltage signal sent to the gate electrode of the device includes a dark component (D (second component)) such as the scattered voltage VT and the reset noise (so-called KTC noise), this voltage signal is It is generally called a dark voltage signal and is known to be a main cause of fixed pattern noise (FPN). Further, hereinafter, for convenience of description, the dark voltage signal is referred to as a “dark voltage signal VD”.

[0086] Also, dark voltage signal VD, the voltage - when sent to the gate electrode of the current conversion MOS transistors QR _1, QR _2, these voltage - drain current conversion MOS transistors QR _1, QR _2, The dark voltage signal V
Current signal corresponding to D (hereinafter, ". Referred to as a dark current signal ID") but is output, this dark current signal ID, these voltage - current conversion MOS transistors QR _1, QR
_{2 A} specific offset current I _off flowing in itself is superimposed.

That is, the combined current signal (second combined current signal) of the dark current signal ID and the offset current I _off is output from the drains of the voltage-current conversion MOS transistors QR ₁ and QR ₂ . Hereinafter, for convenience of description, the combined current signal is referred to as a “dark combined current signal (ID + I _off )”.

The dark combined current signal (ID + I _off ) output from the drains of the voltage-current converting MOS transistors QR ₁ and QR ₂ is connected to the connection lines 20a ₁ and 20b.
_Flow to ₁ . This is because the drive pulse φS is low level,
Since the MOS transistors QB ₁ and QB ₂ for separation switches are non-conductive (open state), the dark combined current signal (ID + I _off) output from the drains of the MOS transistors QR ₁ and QR ₂ for voltage-current conversion. ) Flows to the connection lines 20a ₁ and 20b ₁ .

Next, in the period t ₁₄ , the drive pulse φD
Is set to a low level, the current storage circuits 20a and 20b operate, and the dark combined current signal (ID + I _off ) sent to the connection lines 20a ₁ and 20b ₁ becomes the current storage circuits 20a and 20b.
a, 20b.

Next, in the period t ₁₅ , the driving pulse φD
Is set to a high level, each of the current storage circuits 20a, 20a
Dark synthetic current signal (ID + I _off ) taken in b
Are stored in the current storage circuits 20a and 20b. Then, the stored dark combined current signal (ID + I _off ) is transferred from each current storage circuit 20a, 20b to each connection line 20a ₁ ,
Flowed to 20b ₁ . The current storage circuits 20a and 20b
The specific configuration and operation of will be described later.

Further, during this period t ₁₅ , the drive pulse φTG1 is set to the low level, and the transfer MOS transistor QT of each pixel 1 in the first row is made conductive (ON). As a result, the charges (signal charges) generated and accumulated in the photodiode PD of each pixel 1 in the first row and corresponding to the incident light accumulated in the photodiode PD of each pixel 1 in the first row ( The electric charge (signal electric charge) transferred to the control region) and received by the gate (control region) after the source follower operation of each amplification transistor QA in the first row.
A voltage signal according to the above is output to the vertical source lines 2a and 2b.

When the charge (charge corresponding to incident light) is transferred to the gate (control area) of each amplification transistor QA, the gate potential of each amplification transistor QA becomes
It rises by the amount of transferred charges. That is, when the charge is transferred to the gate (control region) of each amplification transistor QA, the gate potential V of the amplification transistor QA is
_GS is expressed as the following equation. V _GS = V _GD + V _{S (} where V _{GD is} the gate voltage before the charge is transferred to the gate (control area) of the amplifying transistor QA (see the equation) V _S = charge / gate capacitance according to incident light)

Further, each amplification transistor Q in the first row
The source follower operation of A raises the potential of the source of each amplification transistor QA by the same amount as the potential V _{GS of} the gate. That is, the source potential V _SS of each amplification transistor QA is expressed by the following equation. V _SS = V _GS −VT, where V _{GS is} the gate potential of each amplification transistor QA after the charge corresponding to the incident light is transferred to the control region of each amplification transistor QA in the first row (see the formula). . VT: Gate-source voltage when the drain current of each amplification transistor QA is IB.

Therefore, the above equation is further expressed as the following equation. _{V SS = V GS -VT ... =} V GD + V S -VT ( see _{∵V GS = V GD + V S} . Equation.) = VRDG + VN + V S -VT ... (∵V GD = VRDG + VN. Equation reference.)

As a result, on the vertical source lines 2a and 2b, the source potential V _SS of each amplification transistor QA is provided.
A voltage signal according to (Equation) is output.

It is known that the value of the gate-source voltage VT in the expression (or expression) varies for each amplification transistor QA as described above. Therefore, in the voltage signals output from the sources of the amplification transistors QA to the vertical source lines 2a and 2b, the scattered voltage VT and the reset noise (so-called K
Composite component (D + S) corresponding to the sum of the dark component (D) due to TC noise) and the signal component (S) due to the transferred charges.
(First component)) is included, this voltage signal becomes
Generally referred to as a composite voltage signal. For convenience of explanation, the composite voltage signal will be referred to as “composite voltage signal (VD + V
S) ".

[0097] Thus, the vertical source lines 2a, the 2b, the combined voltage signal (VD + VS) is output, the voltage - is sent to a gate electrode of the current conversion MOS transistors QR _1, QR _2.

When the combined voltage signal (VD + VS) is sent to the gate electrodes of the voltage-current conversion MOS transistors QR ₁ and QR ₂ , the voltage-current conversion M is generated.
From the drains of the OS transistors QR ₁ and QR ₂ , a current signal (hereinafter, referred to as “photosynthesis current signal (ID + IS)”) corresponding to the synthesized voltage signal (VD + VS) is output. This photosynthesis current signal (ID + IS) ) Has
These voltage-current conversion MOS transistors QR ₁ , Q
A specific offset current I _off flowing in R ₂ itself is superimposed.

That is, the combined current signal (first combined current signal) of the photo combined current signal (ID + IS) and the offset current I _off is output from the drains of the voltage-current converting MOS transistors QR ₁ and QR ₂ . Hereinafter, for convenience of explanation, the combined current signal is referred to as “light and dark combined current signal (ID +
IS + I _off ) ".

Therefore, during this period t ₁₅ , the current storage circuits 20a and 20b are connected to the connection lines 20a ₁ and 20b.
_The dark synthetic current signal (ID + I _off ) flowing to ₁ is
Only the photocurrent signal IS, which is subtracted from the photodark combined current signal (ID + IS + I _off ), is the MO for each separation switch.
It is output to the S transistors QB ₁ and QB ₂ . That is, the light and dark combined current signal (ID + IS + I _off ) -dark combined current signal (ID + I _off ) can be obtained by simply superposing both signals.
) = Photocurrent signal IS is subtracted.

Further, during this period t ₁₅ , the drive pulse φS is set to the high level, the MOS transistors QB ₁ and QB ₂ for separation switch are made conductive (closed), and the photocurrent signal IS is read out horizontally. MO for switch
It is output to the S transistors QH ₂₁ and QH ₂₂ .

Then, at the end of the period t ₁₅ , the drive pulse φTG 1 is set to the high level, and each transfer MOS transistor QT on the first row is turned off (OFF).

Next, in the period t ₁₆ , the horizontal scanning circuit 7 sequentially outputs the drive pulses φH 1 and φH 2 (to the high level), and the horizontal read switch MOS transistors QH ₁₁ and QH ₁₂ are sequentially turned on (ON). And the photocurrent signal IS (video signal) is sequentially read out from the horizontal read line 8
a is read.

When the horizontal read switch MOS transistor QH ₁₁ is being scanned by the drive pulse φH 1, the inverting inverter 21b operates to bring the shunt MOS transistor QH ₂₂ into conduction with the bias power supply VR, thereby separating the switch. MOS transistor through the QB ₂ offset current I _off voltage and outputs a photocurrent signal iS that has been removed - current conversion MOS transistor QR ₂
Prevents saturation.

Of course, when the horizontal read switch MOS transistor QH ₁₂ is being scanned by the drive pulse φH 2, the inverting inverter 21a operates to bring the shunt MOS transistor QH ₂₁ into conduction with the bias power supply VR, thereby separating the switch. The voltage-current conversion MOS transistor QR that outputs the photocurrent signal IS from which the offset current I _off has been removed via the MOS transistor QB _1.
Saturation of ₁ is prevented.

As described above, since the video signal output to the horizontal read line 8a is the photocurrent signal IS, even if there is a parasitic capacitance on the horizontal read line 8a as in the conventional solid-state image pickup device, this parasitic signal is generated. Since it is not necessary to charge the capacitance and then reset the parasitic capacitance, the read operation of the video signal can be speeded up.

Even if there is a parasitic capacitance on the horizontal read line 8a, since the output video signal is a current,
Charge distribution due to parasitic capacitance is eliminated, and the S /
The N ratio will not deteriorate.

The photocurrent signal IS is output as the drain current of each of the voltage-current conversion MOS transistors QR ₁ and QR ₂ , and the photovoltage signal VS is generally the photocurrent signal IS. MOS transistor that operates in the saturation region when converted to
Transistor QR _1, the voltage of QR ₂₎ - current characteristic is known to become square characteristics.

Therefore, the drain current (photocurrent signal I) of each of the voltage-current conversion MOS transistors QR ₁ and QR ₂ is
S) is also each voltage-current conversion MOS transistor QR
_1, increases with the rise of the gate-source voltage of QR ₂ becomes a (proportional the square) to be, the voltage - source of the current conversion MOS transistors QR _1, QR ₂ are each resistor R _1, Since it is AC-grounded through R ₂ , each voltage-current conversion MOS transistor QR ₁ , Q
Even if the gate voltage of R ₂ rises, the voltage drop in the resistors R ₁ and R ₂ suppresses the increase in the gate-source voltage of each of the voltage-current converting MOS transistors QR ₁ and QR ₂ . That is, the so-called negative feedback effect works.

As a result, the drain currents of the voltage-current conversion MOS transistors QR ₁ and QR ₂ (photocurrent signal I
The relationship between S) and the gate voltage (photovoltage signal VS) is approximately linear, and the photocurrent signal IS corresponding to the photovoltage signal VS is obtained.
(Video signal) can be obtained. That is, if the gate voltages of the voltage-current converting MOS transistors QR ₁ and QR ₂ are constant, the drain current (photocurrent signal IS) is also constant.

Further, the photocurrent signal IS sequentially output to the horizontal read line 8a is amplified and output while being converted into the photovoltage signal VS 'by the current-voltage conversion amplifier circuit 9. Since the input of the voltage conversion circuit 9 is virtually grounded to the constant power source VR, the video signal is output to the output terminal V.
When output from O, the potential of the horizontal read line 8 does not change.

Further, in this embodiment, since the video signal read to the horizontal read line 8a is treated as a current, the current-voltage conversion amplifier circuit 9 can have a low input impedance, and the output video signal is external. The influence of induced noise from can be suppressed.

Next, in the period t ₁₇ , the drive pulse φRS
When V becomes high level, reset switch MOS
The transistors TR _V1 and TR _V2 are turned on (turned on). As a result, the source of each amplification transistor QA and each voltage-current conversion MOS transistor QR ₁ , QR ₂
The gates (control regions) of the vertical source lines 2a, 2b
And reset switch MOS transistors TR _V1 and T
_Grounded via R _V2 .

Next, in the period t ₁₈ , the drive pulse φRD
When 1, φRG and φTG1 are sequentially set to the low level, each reset MOS transistor QP and each transfer MOS transistor QT are rendered conductive (ON). As a result,
The photodiodes PD are reset via the reset MOS transistors QP and the transfer MOS transistors QT.

Further, at the end of the period t ₁₈ , the drive pulse φTG1 is set to the high level again, and each photodiode PD is again in the state of generating and accumulating the charge according to the incident light, and the first row The scanning of pixel 1 of is completed.

The first for the periods t _{11 to} t ₁₈ shown above
The readout operation of the pixels in the row is similarly repeated for the pixels in the second row in the periods t _{21 to} t ₂₈ . In this embodiment, the pixel not having the gate electrode for controlling the control area of the amplifying transistor QA by capacitive coupling has been described as an example, but the control area of the amplifying transistor QA is capacitively coupled. It goes without saying that the same can be applied to a pixel provided with a gate electrode for controlling.

FIG. 3 is a schematic configuration schematic circuit diagram showing an example of the inside of the current storage circuits 20a and 20b shown in FIG. In addition, in FIG. 3, in order to facilitate the explanation,
The two current storage circuits 20a and 20b shown in FIG.
Only 20a of these are shown. Further, the same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

As shown in FIG. 3, the current storage circuit 20a.
Is a constant current MOS transistor QD (P channel)
And a current storage switch MOS transistor QS (P channel) and a voltage storage capacitor CL.

MOS transistor Q for current memory switch
The gate electrode of S is connected to the drive pulse generation circuit 22 via the clock line 22a, the drain is connected to the drain of the constant current MOS transistor QD, and the source is the gate electrode of the constant current MOS transistor QD and the voltage accumulation. Is connected to one electrode of the capacitor CL.

The source of the constant current MOS transistor QD is connected to the power supply voltage VDD (positive), and the other electrode of the voltage storage capacitor CL is grounded.

Next, the operation of the current storage circuit 20a will be described with reference to FIG. For convenience of explanation, the period t ₁₄ after the dark combined current signal (ID + I _off ) is passed from the voltage-current conversion circuit QR ₁ to the connection line 20a ₁ will be described. That is, in the period t ₁₃ in FIG. 2, the drive pulse φRSV is set to the low level, the reset switch MOS transistors TR _V1 and TR _V2 are brought into the non-conducting state (OFF), and each amplification transistor QA in the first row is turned on. A follower operation is performed, and a dark voltage signal (VD) corresponding to the potential of the source at this time is sent to the gate electrodes of the voltage-current conversion MOS transistors QR ₁ and QR _{2 and} the voltage-
The dark combined current signal (ID + I _off ) is supplied from the current conversion MOS transistors QR ₁ and QR ₂ to the connection lines 20a ₁ and 2
A description will be given after the flow to 0b ₁ .

In FIG. 2, the driving pulse φD is set to the low level in the period t ₁₄ . This is a state in FIG. 3 in which the drive pulse φD is sent from the drive pulse generation circuit 22 and the drive pulse φD is given to the gate electrode of the current storage switch MOS transistor QS.

When the drive pulse φD is applied to the gate electrode of the current memory switch MOS transistor QS, the current memory switch MOS transistor QS is turned on (closed), and the voltage-current conversion circuit QR ₁
The dark combined current signal (ID + I _off ) flowing from the connection line 20a ₁ to the connection line 20a ₁ flows (takes in) to the drains of the current storage switch MOS transistor QS and the constant current MOS transistor QD.

The dark combined current signal (ID + I _off ) flowing toward the drain of the current memory switch MOS transistor QS also flows to the source. This is because the current storage switch MOS transistor QS is in a conductive state (closed state).

Therefore, the dark composite current signal (ID + I
_Off ) is eventually passed through both the constant current MOS transistor QD and the current storage switch MOS transistor QS. However, the source of the current memory switch MOS transistor QS is the constant current MOS transistor Q
It is connected to the gate electrode of D and the voltage storage capacitor CL. Therefore, in the steady state, no current flows through the current storage switch MOS transistor QS, and only the dark combined current signal (I
The gate (control region) of the constant-current MOS transistor QD is automatically biased so that D + I _off ) flows and is in an equilibrium state. The gate voltage of the constant current MOS transistor QD at this time is the voltage storage capacitor C.
It is stored in L.

Therefore, the application of the drive pulse φD to the gate electrode of the current memory switch MOS transistor QS is stopped, and the current memory switch MOS transistor Q is stopped.
Even when S is in a non-conducting state (open state) (period t ₁₅ in FIG. 2), since the gate voltage of the constant current MOS transistor QD does not change, the constant current MOS transistor QD does not change.
The dark combined current signal (ID + I _off ) continues to flow from the drain of D to the connection line 20a ₁ .

That is, in general, if the gate-source voltage of the field effect transistor (FET) is constant, the value of the drain current does not change. here,
The gate voltage of the constant current MOS transistor QD is kept constant by the voltage storage capacitor CL, and the source of the constant current MOS transistor QD is the power supply voltage VDD.
Since it is held constant by (positive), a constant current MOS
The gate-source voltage of the transistor QD is constant.

Therefore, the value of the drain current of the constant current MOS transistor QD at this time does not change. The drain current of the constant current MOS transistor QD is the dark combined current signal (ID + I _off ) supplied through the connection line 20a ₁ .

Since the source of the constant current MOS transistor QD is connected to the power supply voltage VDD (positive),
The source side of the constant current MOS transistor QD has a higher potential than the drain side of the transistor QD.

As a result, the dark combined current signal (ID + I _off ) flown from the drain of the voltage-current conversion circuit QR ₁ through the connection line 20a ₁ is used as the drain current of the constant current MOS transistor QD. Q
It flows from the drain of D to the connection line 20a ₁ and then to the drain of the voltage-current conversion circuit QR ₁ . That is, the dark combined current signal (ID + I _off ) is stored in the current storage circuit 20a as the drain current of the constant current MOS transistor QD.

Next, in the period t ₁₅ shown in FIG. 2, the drive pulse φTG1 is set to the low level and is generated in the photodiode PD to the gate (control area) of the amplifying transistor QA, which corresponds to the incident light accumulated therein. The charge is transferred, and the source follower operation causes the combined voltage signal (VD +
VS) is each voltage-current conversion MOS transistor QR
_1, sent to the gate electrode of the QR _2, each voltage - drain current conversion MOS transistors QR _1, QR _2, light dark combination current signal (ID + IS + I _off) is output.

Then, as shown in FIG. 3, the stored dark combined current signal (ID + I _off ) flowing from the current storage circuit 20a to the drain of the voltage-current conversion MOS transistor QR ₁ through the connection line 20a _1. ) Is subtracted from the light-dark combined current signal (ID + IS + I _off ) output from the drain of the voltage-current converting MOS transistor QR ₁ ((ID + IS + I _off ) − (ID + I _off ) = I
S), driving pulses φH1 and φH2 are sequentially transmitted from the horizontal scanning circuit 7 during the period t ₁₆ shown in FIG. 2, and the horizontal read switch MOS transistors QH ₁₁ and QH ₁₂ are sequentially scanned (turned on) to subtract. Only the subsequent photocurrent signal IS is separated MOS transistors QB ₁ and QB ₂ and horizontal read switch MOS transistors QH ₁₁ and
The horizontal read line 8a is output via QH ₁₂ .

In the above embodiments, the case where the amplifier section (amplification transistor QA) of the pixel 1 is used as a JFET has been described as an example, but the present invention is not limited to this, and MOS transistors and Even in the case of a bipolar transistor, any element that can control the output voltage of the drain or collector, the source, or the emitter by the voltage of the control electrode such as the gate or the base can be similarly applied, and these may be used in combination.

Therefore, the MOS type static induction transistor (SIT) shown in the conventional example is used as a pixel or AM.
Amplification type solid-state imaging devices such as I and CMD can also be applied in the same manner, but MOS type static induction transistor (SI
When T) is used as a pixel, or when the above-described embodiment is applied to an amplification type solid-state imaging device such as AMI or CMD, a pixel having a structure in which a photoelectric conversion element and an amplification element are separated cannot be used. A method similar to that described in the example, that is, a dark voltage signal VD is first output, then a combined voltage signal VD + VS is output, and the former is subtracted from the latter cannot be adopted.

Therefore, when a MOS static induction transistor (SIT) is used as a pixel or an amplification type solid-state image pickup device such as AMI or CMD is used, first, like the solid-state image pickup device described in the conventional example, first. Composite voltage signal VD +
VS is output, and the light-dark combined current signal (ID + IS + I _off ) corresponding to this combined voltage signal VD + VS is stored in the current memory circuit, and then the dark voltage signal VD is output to output the dark combined current signal (ID + I _off ). And the signals are superimposed so that the latter is subtracted from the former. Thereby, the video signal from which the fixed pattern noise (FPN) has been removed can be read at high speed.

FIG. 4 is a schematic circuit diagram showing a schematic structure of a solid-state image pickup device according to the second embodiment of the present invention. The first
The difference from the embodiment is that the MOS type static induction transistor (M
OSSIT (hereinafter, simply referred to as “SIT transistor”) S ₁₁ , S ₁₂ , S ₂₁ , and S ₂₂ .
In order to omit redundant description, the same parts as those of the solid-state imaging device described in the first embodiment (FIG. 1) and the conventional example (FIG. 6) are designated by the same reference numerals and the description thereof will be omitted.

In the solid-state image pickup device shown in FIG. 4, pixels S ₁₁ ,
Since S ₁₂ , S ₂₁ , and S ₂₂ are SIT transistors, it is difficult to output the combined voltage signal VD + VS after outputting the dark voltage signal VD as in the first embodiment (FIG. 1). . Therefore, when the SIT transistor is used as a pixel, first, similarly to the conventional example (FIG. 6), the drive pulse φG of the read level VG ₂ is given to the pixel of the row selected by the vertical scanning circuit 6.

As a result, the combined voltage signal (VD + VS) output from the selected pixel is the vertical source line 2a,
Each voltage-current conversion MOS transistor Q via 2b
It is sent to the gate electrodes of R ₁ and QR ₂ and the combined voltage signal (V
It is converted into a photosynthesis current signal (ID + IS) corresponding to D + VS). At this time, each voltage-current conversion MOS
The offset current I _off peculiar to the transistors QR ₁ and QR ₂ itself is superposed, and finally, the light-dark combined current signal (ID + IS + I _off ) is output from each of the voltage-current conversion MOS transistors QR ₁ and QR ₂ to store the current. Circuit 2
It is stored in 0a and 20b.

Next, the drive pulse φ of the reset level VG ₃ is applied to the pixels in the row selected by the vertical drive circuit 6.
G is applied, the drive pulse φRV is set to a high level to make the reset MOS transistors TR _V1 and TR _V2 conductive (ON state), the source lines 2a and 2b are grounded, and the pixel (the pixel of the selected row) is grounded. ) Is reset.

Next, the reset MOS transistor TR
_{The V1} and TR _V2 are turned off (OFF), the drive pulse φG is set to the read level VG ₂ again, and the dark voltage VD after resetting the pixel is output. As a result, the pixels S ₁₁ , S ₁₂ ,
The dark voltage signal VD is sent from S ₂₁ , S ₂₂ to the gate electrodes of the voltage-current conversion MOS transistors QR ₁ , QR ₂ via the vertical source lines 2a, 2b, and the dark voltage signal VD is sent.
Is converted into a dark current signal ID corresponding to
Each voltage-current conversion MOS transistor QR ₁ , QR ₂
A specific offset current I _off flowing through itself is superimposed,
After all, each voltage-current conversion MOS transistor QR ₁ ,
A dark synthetic current signal (ID + I _off ) is output from QR ₂ .

Therefore, the voltage-current conversion MOS transistors QR ₁ and QR _{2 are} supplied from the current storage circuits 20a and 20b.
Since the light / dark combined current signal (ID + IS + I _off ) is flown to the light-dark combined current signal (ID + I _off ) + light / dark combined current signal (ID + IS + I).
_off ) = photocurrent signal (-IS) is subtracted.

Then, the horizontal read switch MOS transistors QH ₁₁ and QB ₁₁ sequentially scanned (on) by the separation switch MOS transistors QB ₁ and QB ₂ and the drive pulses φH 1 and φH 2 sequentially sent from the horizontal scan circuit 7.
Only the photocurrent signal (-IS) after subtraction via QH ₁₂
The horizontal read line 8a is output.

As a result, as in the first embodiment, the video signal output to the horizontal read line 8 is the photocurrent signal (-).
Therefore, even if there is a parasitic capacitance on the horizontal read line 8, it is not necessary to charge this parasitic capacitance and then reset it, and the video signal read operation can be speeded up.

Further, since the video signal is a current signal, charge distribution due to the parasitic capacitance is eliminated, and the output level of the video signal does not drop, so that the S / N ratio of the video signal does not deteriorate.

Also in the second embodiment, the current-voltage conversion amplifier circuit 9 whose input is virtually grounded to the constant power source VR is also provided.
Since the horizontal read line 8 is provided, when the video signal is output from the output terminal VO, the horizontal read line 8
Does not change.

Also in the second embodiment, since the video signal read out to the horizontal read line 8 is treated as a current, the current-voltage conversion circuit 9 can have a low input impedance and the output video signal. Can suppress the influence of externally induced noise.

FIG. 5 is a schematic circuit diagram showing a schematic structure of a solid-state image pickup device according to the third embodiment of the present invention. Differs from the solid-state imaging device according to the first embodiment described with reference to FIG. 1, the vertical source lines 2a, the 2b, the combined voltage signal storage capacitor CS ₁ having one electrode grounded, CS ₂
And these combined voltage signal storage capacitors CS ₁ and CS
_The point is that switching MOS transistors QW ₁ and QW ₂ for controlling charge / discharge of ₂ are provided. The same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof will be omitted.

As described above, the combined voltage signal accumulating capacitors CS ₁ and CS ₂ and the switching MOS transistor QW.
₁ and QW ₂ are provided in the solid-state imaging device described with reference to FIG. 1 after the charge is transferred from the photodiode PD to the gate (control area) of the voltage amplification transistor QA, and then each voltage amplification transistor is provided. The charges held in the gate (control area) of QA are simultaneously generated by the combined voltage signal (VD + V
However, in reality, when a video signal is output (the period t ₁₆ or the period t ₂₆ shown in FIG. 2), the pixel is closer to the vertical scanning circuit 6 through the vertical source line. It is output sequentially.

Therefore, until the charges transferred to the gate (control area) of the voltage amplification transistor QA of the pixel arranged at the farthest position from the vertical scanning circuit 6 are output as the combined voltage signal (VD + VS). The voltage is held in the gate (control area) of the voltage amplification transistor QA for the longest time.

Therefore, the combined voltage signal (VD + VS) output from the voltage amplification transistor QA of the pixel closest to the vertical scanning circuit 6 and the voltage amplification of the pixel arranged farthest from the vertical scanning circuit 6 are used. It is conceivable that the combined voltage signal (VD + VS) output from the transistor QA may have different values.

That is, it is conceivable that a dark current also flows in each voltage amplifying transistor QA itself, and this dark current causes the gate voltage of the voltage amplifying transistor QA to differ, resulting in a composite voltage signal (VD + VS). It is possible that the values differ.

Then, if the combined voltage signal VD + VS output from the voltage amplification transistor QA of the pixel closest to the vertical scanning circuit 6 and the voltage amplification transistor of the pixel arranged farthest from the vertical scanning circuit 6. When the value of the synthesized voltage signal VD + VS output from QA becomes different, the current storage circuit 20a, dark combination current signal stored is output (ID + I _off) voltage 20b - from current conversion MOS transistors QR ₁ Even if subtracted from the output light-dark combined current signal (ID + IS + I _off ),
It is possible that the S / N ratio of the video signal deteriorates.

In order to solve the above problems, the vertical source lines 2a and 2b are provided with combined voltage signal storage capacitors CS ₁ and CS ₂ and switching MOS transistors QW ₁ and QW ₂ , respectively, and the photodiode PD Immediately after the charge is transferred from the voltage amplifying transistor QA to the gate (control area) of the voltage amplifying transistor QA, the composite voltage signal (VD + VS) is output from each voltage amplifying transistor QA, and the composite voltage signal accumulating capacitors CS ₁ and CS ₂ are output. Accumulate in.

In this way, when the video signal is output (see FIG.
In the period t ₁₆ or the period t ₂₆ shown in FIG. 5, the value of the combined voltage signal VD + VS does not change even when sequentially read from the vertical source lines of the pixels close to the vertical scanning circuit 6, so that the S / N ratio of the video signal It is possible to prevent deterioration.

Further, when the switch MOS transistors QW ₁ and QW ₂ are turned off (OFF) after the combined voltage signal (VD + VS) is accumulated in the combined voltage signal accumulating capacitors CS ₁ and CS ₂ , the combined voltage signal accumulation is performed. Since the capacitors CS ₁ and CS ₂ are in a floating state, the constant current sources 12a and 12b can be cut off (OFF) during this period to reduce power consumption.

FIG. 6 is a schematic circuit diagram showing a schematic structure of a solid-state image pickup device according to the fourth embodiment of the present invention. This fourth
The solid-state image pickup device according to the embodiment is similar to the solid-state image pickup device described in FIG.
In addition, dark voltage signal storage capacitors CD ₁ and CD ₂ whose one electrodes are grounded, and switching MOS transistors QW ₁ and QW for controlling charging and discharging of these dark voltage signal storage capacitors CD ₁ and CD _{2. 2} is provided,
Each pixel including a photoelectric conversion unit MOS type static induction transistor (MOSSIT (hereinafter, simply referred to as "SIT transistor".)) That is set to _{S 11, S 12, S 21} , S 22 differs from the other embodiments It is a point. The same parts as those in FIG. 4 are designated by the same reference numerals and the description thereof will be omitted.

In the solid-state image pickup device shown in FIG. 6, the pixels S ₁₁ ,
Since S ₁₂ , S ₂₁ , and S ₂₂ are SIT transistors, it is difficult to first output the dark voltage signal VD and then the combined voltage signal (VD + VS). Therefore,
When the SIT transistor is used as a pixel, first, similarly to the conventional example, first, the drive pulse φG of the read level VG ₂ is applied to the pixel in the row selected by the vertical scanning circuit 6, and the pixel in the selected row is selected. From composite voltage signal (VD + V
S) the vertical source lines 2a, and outputs to 2b, the voltage - current conversion MOS transistors QR _1, photosynthetic current signal corresponding to the combined voltage signal VD + VS by QR ₂ (ID +
IS) and the offset current I _off of the light-dark combined current signal (ID + IS + I _off ) to the current storage circuits 20a and 20b.
To memorize.

Next, the drive pulse φ of the reset level VG ₃ is applied to the pixels in the row selected by the vertical drive circuit 6.
G is applied to reset the pixels (pixels in the selected row). As a result, the dark voltage signal VD is output from the pixels S ₁₁ , S ₁₂ , S ₂₁ , and S ₂₂ , the dark voltage signal VD is stored in the dark voltage signal storage capacitors CD ₁ and CD ₂ , and then the driving pulse Generating circuit 51 to clock line 51
via a sends a drive pulse φXV the gate electrode of the switching MOS transistor QW _1, QW _2, the MOS transistor QW _1, QW ₂ for the switch to cut-off state (OFF).

By doing so, as in the solid-state image pickup device according to the third embodiment described with reference to FIG. 5, the vertical scanning circuit is operated at the time of outputting a video signal (period t ₁₆ or period t ₂₆ shown in FIG. 2). Since the value of the combined voltage signal (VD + VS) does not change even when sequentially read from the vertical source lines of pixels close to 6, the deterioration of the S / N ratio of the video signal can be prevented.

Further, the switching MOS transistor QW
_{Since 1} and QW ₂ are in the cutoff state (OFF) and the dark voltage signal storage capacitors CD ₁ and CD ₂ are in the floating state, the constant current sources 12a and 12b are in the cutoff state (OFF) during this period. It is also possible to reduce power consumption.

In the above embodiments, the voltage-current converting MOS transistors QR ₁ and QR ₂ are described as depletion type MOS transistors, but they may be enhancement type MOS transistors or junction type field effect transistors.

[0162]

As described above, according to the present invention, either one of the voltage signals composed of the first component or the second component output from the plurality of pixels is converted into the current signal by the voltage-current conversion means and converted. A current signal corresponding to the sum of the current signal and the offset current peculiar to the voltage-current conversion means itself is stored in the current storage means, and subsequently the voltage signal including the first component or the second component output from the pixel. One of the other is converted into a current signal by the voltage-current converting means, and the current signal corresponding to the sum of the converted current signal and the offset current peculiar to the voltage-current converting means itself and already stored in the current storing means. Since a voltage signal (video signal) consisting of a component according to the amount of incident light by subtraction from the current signal is converted into a current signal and output, a horizontal capacitance does not occur in the horizontal readout line, and this Or charges the parasitic capacitance, it is possible to omit the time for resetting, there is an effect that it is possible to speed up the reading operation of the video signal.

Further, according to the present invention, since the video signal read out to the horizontal read line is a current signal, the charge is not distributed by the parasitic capacitance, so that the S / N ratio of the video signal can be improved. is there.

Further, according to the present invention, since it is not affected by the parasitic capacitance of the horizontal read line, the performance is not deteriorated even if the number of pixels is increased, and it is easy to increase the number of pixels.

Further, in the present invention, since the output circuit can have a low input impedance, there is an effect that the induction noise can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic circuit diagram showing a schematic configuration of a solid-state imaging device according to an embodiment of the present invention.

FIG. 2 is a pulse timing chart for explaining the operation of the solid-state imaging device according to the first embodiment of the present invention shown in FIG.

FIG. 3 is a schematic configuration schematic circuit diagram showing the inside of a current storage means according to an embodiment of the present invention.

FIG. 4 is a schematic circuit diagram showing a schematic configuration of a solid-state imaging device according to a second embodiment of the present invention.

FIG. 5 is a schematic circuit diagram showing a schematic configuration of a solid-state imaging device according to a third embodiment of the present invention.

FIG. 6 is a schematic circuit diagram showing a schematic configuration of a solid-state imaging device according to a fourth embodiment of the present invention.

FIG. 7 is a schematic circuit diagram showing a schematic configuration of a conventional general solid-state imaging device.

FIG. 8 is a pulse timing chart for explaining the operation of the conventional solid-state imaging device shown in FIG.

[Explanation of symbols]

PD: photodiode (photoelectric conversion element) QA: Voltage amplifier transistor (amplifying element) QT: transfer MOS transistors (transfer control device) QP: reset MOS transistor (reset element) QR _1, QR _2: Voltage - current conversion MOS transistors (voltage / current conversion means) QH ₁₁ , QH ₁₂ : horizontal read switch MOS transistors (switching means) QH ₂₁ , QH ₂₂ : shunt MOS transistors (switching means) QB ₁ , QB ₂ : isolation switch MOS transistors (Switching means) 2a, 2b: Vertical source line (vertical read line) 8a: Horizontal read line (horizontal read line) 8b: Bias line (horizontal read line) 20a, 20b: Current storage circuit (current storage means)

Claims (2)

[Claims] 1. A plurality of pixels which are arranged in a two-dimensional matrix and which convert charges corresponding to incident light into voltage signals and output the voltage signals, and the pixels are sequentially scanned in the column direction in common for each row of the matrix arrangement. A plurality of vertical readout lines for extracting the voltage signal from each pixel for each column, and a horizontal for sequentially extracting the time-series voltage signals for each row by scanning the plurality of vertical readout lines in the row direction. A solid-state imaging device including a read line, wherein each vertical read line has an amount of incident light output from a pixel connected to each pixel at different times when the pixel is sequentially scanned for each row, and A voltage-current conversion unit that outputs a current signal corresponding to each of the voltage signal including the first component corresponding to the sum of the dark outputs and the voltage signal including the second component corresponding to the dark output is provided, and each voltage-current conversion unit is provided. On the output side of the means, the voltage A first combined current signal according to the sum of an offset current specific to the current conversion means and a current signal corresponding to the voltage signal composed of the first component, and an offset current specific to the voltage / current conversion means and the second component Current storing means for storing one of the second combined current signals corresponding to the sum of the current signal corresponding to the voltage signal and the current signal corresponding to A current signal composed of a component corresponding to the amount of incident light is subtracted from the other one of the first combined current signal and the second combined current signal and the combined current signal already stored in the current storage means to the horizontal readout line. A solid-state image pickup device comprising switching means for reading each. 2. The photoelectric conversion element for generating and accumulating charges according to incident light, the amplification element for generating a voltage signal according to the charges received in the control region, and the photoelectric conversion element generated and accumulated by the photoelectric conversion element. 2. The transfer control element for selectively transferring the accumulated charge to the control region of the amplification element, and the reset control element for selectively resetting the charge of the control region of the amplification element. Solid-state imaging device.