JPS6316910B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to charge coupled devices, and more particularly to improvements in bias charge injection methods in charge coupled devices having a multi-channel structure.

Conventionally, a dual channel structure has been known as a structure of a transfer section of a device to which a charge-coupled device is applied, such as a delay line or a one-dimensional image sensor. When comparing the above structure with a monochannel structure assuming that the repetition frequency of the transfer pulses supplied to the transfer section is the same, the Nyquist limit is doubled, and the number of transfer stages and power consumption to obtain the same delay time are doubled. 1. However, conventional dual-channel charge-coupled devices have a drawback in that each channel has an individual input/output section, resulting in differences in input/output characteristics between the channels.

A method to overcome this drawback is to use a first charge input with a common charge input and a single output for each transfer channel.
A dual-channel charge-coupled device as shown in the figure was proposed. That is, the charge input section common to the transfer channel is composed of an input diode 11, dual input gate electrodes 12 and 13, and a switching gate electrode 14, and the output section is composed of a floating diffusion layer 15 and an output amplifier 16 common to the channels. It is configured. 17 and 18 are first electrodes of the transfer channel. As a typical charge injection method, a potential balancing method is well known in which a sampling pulse is applied to the input diode 11, a signal and DC bias is applied to the input gate electrode 12, and a DC bias is applied to the input gate electrode 13. The accumulated signal charge and bias charge are alternately injected into the two transfer channels by applying a pulse to the switching gate electrode 14 that is synchronized with the transfer pulse applied to the first electrodes 17 and 18 of the transfer channel. . The signal charges and bias charges transferred through the two transfer channels alternately change the potential of the floating diffusion layer 15, and this change is detected by the output amplifier 16. FIG. 2 is a diagram for explaining the output section of the dual channel charge coupled device shown in FIG. 1, where 21 is the final electrode of transfer channel A;
22 is the final electrode of the transfer channel B, 23 is the output terminal, and the same numbers as in FIG. 1 indicate the same items. As shown in the figure, there are various coupling capacitances in the output section. For example, there is a coupling capacitance between the final electrode 21 of transfer channel A and the floating diffusion layer 15.
Similarly, C ₁ has a coupling capacitance between it and the output amplifier 16.
A coupling capacitance C ₃ exists between C ₂ and the output terminal 23 . Similarly, for transfer channel B, there is a coupling capacitance between the final electrode 22 and the floating diffusion layer 15.
A coupling capacitance C ₂ ′ exists between C ₁ ′ and the output amplifier 16.
A coupling capacitance C ₃ ' exists between the output terminal 23 and the output terminal 23. These are only a small portion of the coupling capacitance present at the output. Here, for simplicity, we will explain the electrode to which the transfer pulse φ ₁ is applied, the floating diffusion layer 15, and the output amplifier 1.
C〓 ₁ is the total coupling capacitance between the electrode 6 and the output section consisting of the output terminal 23, etc., and the total coupling capacitance between the electrode to which the transfer pulse φ2 is applied and the output section is C〓 1 .
If C〓 ₂ , generally C〓 ₁ ≠ C〓 ₂ , so the influence of transfer pulse φ ₁ or transfer pulse φ ₂ on the output signal waveform is different, and as shown in Fig. 3, the influence of the output signal waveform is A difference occurs in the output level.
This means that the output signal contains a component of the clock pulse frequency (Nyquist limit). The effect that the transfer pulse has on the output signal waveform becomes more pronounced as its repetition frequency increases, and this becomes a major problem when applying charge-coupled devices to fields that require high-frequency operation, such as TV video signal processing. Become.

In the structure shown in Figure 1, variations in the output voltage of each transfer channel due to differences in input/output sections are eliminated, but variations in output voltage that occur due to differences in dark current and transfer efficiency between each transfer channel are eliminated. Also, the variation in output voltage due to the coupling capacitance of the output section explained in Figures 2 and 3 cannot be improved by the driving method of the charge-coupled device, and the extent of the variation can only be determined by the manufacturing process of the charge-coupled device. In the worst case, there was a difference of about 20% between the output voltages of each transfer channel.

An object of the present invention is to eliminate such conventional drawbacks and provide a multi-channel charge-coupled device with less variation between transfer channels.

According to the invention, the input diode and the first
and a charge input section composed of a second input gate electrode and a switching gate electrode, and a charge transfer channel that divides signal charges from the charge input section into a plurality of columns and transfers them using transfer pulses having different phases, respectively. In the charge-coupled device having a charge output section that synthesizes and outputs signal charges from the plurality of rows of charge transfer channels, one of the first and second input gate electrodes is connected to one of the plurality of rows of charge transfer channels. The divided input gate electrodes are divided so that independent electrical signals are applied thereto, and different electrical signals are applied to each of the divided input gate electrodes so that variations in the signal output voltage from the plurality of charge transfer channels are corrected. A charge-coupled device characterized in that a DC bias voltage is applied is obtained.

A multi-channel charge coupled device according to the present invention will be described below with reference to the drawings.

FIG. 4 shows an embodiment of the present invention.
Reference numerals 1a and 41b indicate input gate electrodes divided into two parts, and a dotted line portion 42 indicates a channel stopper. Further, 43 represents a voltage source for applying a DC bias to the input gate electrodes 41a and 41b, and 44 represents a variable resistor for adjusting the DC bias applied to the input gate electrodes 41a and 41b. The same numbers as in FIG. 1 indicate the same things.

Next, the operation of this embodiment will be explained. First, for charge injection, a potential balancing method is used in which a sampling pulse is applied to the input diode 11, different DC biases are applied to the input gate electrodes 41a and 41b, and a signal and DC bias are applied to the input gate electrode 13. Signal charges and bias charges are accumulated below 13. Next, since the transfer pulses φ ₁ and φ ₂ having a phase difference of 180° are applied to the first electrodes 17 and 18 of the transfer channel, a pulse synchronized with the above two transfer pulses is applied to the switching gate electrode 14. As a result, charges accumulated in regions 45 and 46 under input gate electrode 13 are alternately injected into transfer channel A and transfer channel B, respectively. FIG. 5 is a diagram showing the relationship between the DC bias applied to the input gate electrodes and the amount of charge injected into the transfer channel.
V _G1 and the amount of charge injected into the transfer channel is Q. Further, V _A and V _B are DC biases applied to the input gate electrodes 41a and 41b, respectively, and Q _A ,
Q _B indicates the amount of charge injected into transfer channels A and B, respectively. The DC bias V _G2 applied to the input gate electrode 13 is constant. As is clear from the figure, the DC biases V _A and V _B applied to the input gate electrodes 41a and 41b are set to different values using the variable resistor 44 in FIG.
Different bias charges Q _A and Q _{B can be injected into the transfer channels A and B} , respectively. Furthermore, as long as the relationship between the DC bias V _G1 and the amount of charge Q injected into the transfer channel shown in FIG. 5 is linear, the amount of signal charge injected into transfer channels A and B for the same input signal level. are equal.

Therefore, if the variable resistor 44 is adjusted so that the output voltage of each transfer channel is uniform, that is, a DC voltage smaller than that of the other transfer channel is applied to the input gate electrode (41a or 41b) corresponding to the transfer channel with the smaller output voltage. When a bias is applied, more bias charge is injected into this transfer channel than other transfer channels, so the dark current of each transfer channel, variations in transfer efficiency, and differences in coupling capacitance at the output section Variations in the output voltage of each transfer channel that occur are corrected, and a uniform output voltage as shown in FIG. 6 can be obtained.

In the configuration shown in FIG. 4, the input gate electrodes 41a and 41b are provided with different DC biases,
Although a signal and a DC bias are applied to the input gate electrode 13, a configuration as shown in FIG. 7 in which the order of these two electrodes is reversed can also provide the same effect as in FIG. 4. 71a, 71b in FIG.
indicates an input gate electrode divided into two, and the fourth
Numbers that are the same as those in the figures indicate the same items.

FIG. 8 shows an embodiment in which the present invention is applied to a three-row transfer channel type charge coupled device.
81a, 81b, 81c are input gate electrodes divided into three; 82 is a first electrode of transfer channel C;
Reference numerals 83a, 83b, and 83c indicate variable resistors for adjusting the DC bias applied to the input gate electrodes 81a, 81b, and 81c, respectively. The same numbers as in FIG. 4 indicate the same parts. In the same figure,
If the variable resistors 83a, 83b, 83c are adjusted so that the output voltage of each transfer channel is uniform, that is, the three variable resistors 83a, 83b are adjusted so that more bias charge is injected into the transfer channel with a lower output voltage. , 83c, the dark current of each transfer channel, variations in transfer efficiency, and variations in output voltage of each transfer channel caused by differences in coupling capacitance at the output section can be corrected.

Similarly, in a charge-coupled device having a multi-channel structure, one input gate electrode of the charge input section is divided in the charge transfer direction by a number equal to the number of transfer channels, and each divided input gate electrode is By applying a direct current bias, effects similar to those in the above case can be obtained.

As explained above, according to the present invention, by injecting an appropriate bias charge to each transfer channel, variations in output voltage caused by differences in dark current and transfer efficiency in each transfer channel, and output A multi-channel charge-coupled device can be obtained in which variations in output voltage caused by differences in coupling capacitance between sections can be corrected.

[Brief explanation of the drawing]

Figure 1 is a conventional dual channel charge coupled device, Figure 2 is an explanatory diagram of the output section in Figure 1, and Figure 3 is a transfer pulse applied to the dual channel charge coupled device in Figure 1 and its output. FIG. 4 is a diagram showing an embodiment in which the present invention is applied to a dual-channel charge-coupled device, and FIG. 5 shows the waveforms of the DC bias applied to the input gate electrode of FIG. 4 and the waveforms injected into the transfer channel. 6 is a diagram for explaining the relationship between the amount of charge, FIG. 6 is an output signal waveform of the dual channel charge coupled device of FIG. 4, FIG. 7 is a diagram for explaining another embodiment of FIG. 4, FIG. 8 is a diagram showing an example in which the present invention is applied to a three-row transfer channel type charge coupled device. In the figure, 11...input diode, 12, 13,
41a, 41b, 71a, 71b, 81a, 81
b, 81c... Input gate electrode, 14... Switching gate electrode, 15... Floating diffusion layer, 16...
...Output amplifier, 17...First electrode of transfer channel A, 18...First electrode of transfer channel B, 21...
...Final electrode of transfer channel A, 22...Final electrode of transfer channel B, 23...Output terminal, 42...
Channel stopper, 43... Voltage source, 44, 8
3a, 83b, 83c...variable resistor, 45, 46
...Charge storage region under the input gate electrode 13, 82
...First electrode of transfer channel C, φ ₁ , φ ₂ , φ ₃ ...
…Transfer pulse, C ₁ , C ₂ , C ₃ , C ₁ ′, C ₂ ′, C ₃ ′...
Coupling capacity.

Claims (1)

[Claims] 1 A charge input section composed of an input diode, first and second input gate electrodes, and a switching gate electrode, and a signal charge from the charge input section is divided into multiple columns and transferred with transfer pulses having different phases. In a charge-coupled device having a charge transfer channel for transferring and a charge output section for combining and outputting signal charges from the plurality of columns of charge transfer channels, one of the first and second input gate electrodes is connected to the charge transfer channel. It is divided so that independent electric signals are applied to each of the plurality of rows of charge transfer channels, and variations in signal output voltage from the plurality of rows of charge transfer channels are applied to each of these divided input gate electrodes. A charge-coupled device characterized by applying different DC bias voltages that are corrected.