JPH0795830B2 - Solid-state imaging device - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a solid-state imaging device, and more particularly to a solid-state imaging device with improved electrical characteristics of an output section.

[Technical background of the invention and its problems]

FIG. 2 shows a conventional solid-state imaging device. As shown in the figure,
The solid-state image pickup device includes light receiving sections 2-1 to 2 arranged in a linear fashion.
7 and the signal charges of the light receiving parts 2-1 to 2-7 are stored in the CCD register 4
Transfer gate 3 to transfer to and CC to transfer signal charges sequentially
The D register 4 and the output section 5 for serially reading out the signal charge of the CCD register 4 to the outside are arranged on the semiconductor substrate 1.

In such a configuration, when the light receiving units 2-1 to 2-7 receive light for a predetermined time (hereinafter, referred to as integration time), a signal corresponding to the amount of light hitting each of the light receiving units 2-1 to 2-7. The charge is accumulated. By opening the transfer gate 3 in this state, the signal charges of the respective light receiving units 2-1 to 2-7 are transferred to and stored in the CCD register 4. A transfer clock is applied to the CCD register 4 from a clock driver (not shown), and the signal charges stored in synchronization with this clock are sequentially transferred as a time series signal and converted into a voltage corresponding to the amount of charge at the output section 5. Then, it is sent to the outside as a time series voltage signal.

By the way, the signal charges generated in the light receiving units 2-1 to 2-7 are proportional to the product of the light amount A and the integration time T. Therefore, the output unit 5
The output voltage V sent to the outside is expressed by V = kGAT (1) where G is the conversion gain of the output section 5. However, k is a proportional constant. This output voltage V is externally subjected to processing such as A / D conversion, but the level of the output voltage V cannot be made too small in consideration of the accuracy of the system configuration in such a case.

Therefore, when the light amount A becomes small, the integration time T is lengthened to secure the required level of the output voltage V, or the output voltage V is amplified outside while keeping the integration time T constant. Either measure came.

However, if the integration time T is lengthened, there is a problem that the number of samplings per unit time is reduced and system efficiency is deteriorated. If an amplifier is arranged outside, the structure becomes complicated.

[Object of the Invention]

The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a solid-state imaging device capable of ensuring a required output voltage.

[Outline of Invention]

In order to achieve this object, a solid-state imaging device according to the present invention includes a light-receiving unit that generates a signal charge according to an input optical signal, a transfer unit that transfers the signal charge generated by the light-receiving unit, and a transfer unit. A conversion unit that converts the transferred signal charge into a voltage signal according to the amount of the charge, an amplification unit that amplifies the output of the conversion unit, and a conversion unit of the conversion unit when the level of the output signal of the conversion unit is high. Switching means for outputting the output to the outside and switching the connection when the level of the output signal of the converting means is low to output the output of the amplifying means to the outside.

Example of Invention

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a solid-state imaging device according to an embodiment of the present invention.
As shown in the figure, a switch is provided on the output side of the output buffer 30.
7, 9 are provided to select whether to directly output the output signal of the output buffer 30 to the output terminal 20 of the output section 5 or to the voltage amplifier 6 arranged on-chip on the semiconductor substrate 1. There is. On the other hand, the switch 8 outputs the output signal of the voltage amplifier 6 to the output terminal of the output section 5.
Has the action of connecting to 20. The switches 7 and 8 are on / off controlled by the control terminal 24, and the switch 9 is on / off controlled by the control terminal 22.

In such a configuration, when the amount of light striking the light receiving units 2-1 to 2-7 is sufficient and a sufficient output voltage is obtained from the output buffer 30, the switch 9 is turned on via the control terminals 22 and 24, and the switch 7 is turned on. Output buffer 3 by turning off
The output voltage of 0 is delivered directly to the output terminal 20. On the other hand, the amount of light striking the light receiving units 2-1 to 2-7 is small, and the output buffer
If the output voltage level from 30 is low, control terminals 22, 24
By turning off the switch 9 and turning on the switches 7 and 8 via the, the output voltage of the output buffer 30 is given to the voltage amplifier 6. As a result, the output voltage of the output buffer 30 is amplified to a sufficient level by the voltage amplifier 6 and sent to the output terminal 20 via the switch 8.

As a result, an output voltage of a level sufficient for external processing can be obtained from the output terminal 20 of the output section 5 regardless of the amount of light entering the light receiving sections 2-1 to 2-7.

In the above embodiment, the case where the number of the voltage amplifier 6 is one is illustrated, but by arranging a plurality of the voltage amplifiers 6, the range of the output voltage can be set more finely.

Further, by combining the configurations of the above-described embodiments, a more flexible and highly safe system can be constructed in consideration of the dynamic range of the voltage amplifier 6.

〔The invention's effect〕

As described above, according to the present invention, the amplification factor of the output section is adjusted in accordance with the magnitude of the signal charge from the charge transfer means, and the output terminal of the output section is always at a level suitable for processing in the subsequent system. It is possible to send the signal of.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a solid-state imaging device according to an embodiment of the present invention, and FIG. 2 is a schematic configuration diagram of a conventional solid-state imaging device. 1 ... semiconductor substrate, 2-1 to 2-7 ... light receiving part, 3 ...
Transfer gate, 4 ... CCD register, 5 ... Output section, 6 ...
… Amplifier, 7,8,9 …… Switch, 20 …… Output terminal, 22,24
...... Control terminal, 30 ...... Output buffer.

Claims (1)

[Claims] 1. A light receiving portion for generating a signal charge according to an input optical signal, a transfer means for transferring the signal charge generated by the light receiving portion, and a signal charge transferred by the transfer means for this charge amount. A converting means for converting the voltage signal into a corresponding voltage signal; an amplifying means for amplifying the output of the converting means; and a converting means for outputting the output of the converting means to the outside when the level of the output signal of the converting means is high. And a switching means for switching the connection and outputting the output of the amplifying means to the outside when the level of the output signal of is low.