JPS5925269A - Charge transfer device - Google Patents

Abstract

PURPOSE:To eliminate the variation of output due to temperature drift by a method wherein the outputs of the first and second output circuits, with the input of charges generated by photo reception or those transferred in light shielding state, are inputted to a differential amplifier. CONSTITUTION:The photo input is transferred as the amount of charges to an MOS transistor 3' under the control by a timing generation circuit 1' through a photo reception and transfer circuit 2'. Further, it is converted into voltage and held to sample in the first output circuit consisting of MOS transistors 3', 5' and a resistor 4', and supplied to the gate of an MOS transistor 6' at the output stage. Besides, the output of a dummy transfer part 20 wherein light is shielded is connected to the gate of an MOS transistor 10 likewise through the second output circuit. Then, the outputs from the first and second output circuits are inputted to the differential amplifier 19 respectively via resistors 15-19, and accordingly an output 8' can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a charge transfer device, and more particularly to a circuit at a cutting stage thereof.

Solid-state imaging devices such as CCD image sensors are devices that convert the intensity of light into voltage, and are widely used as document reading devices in facsimiles and the like.

No. 11\1 is a circuit diagram of a conventional COD sensor.

The light input passes through the light receiving and transferring circuit 2 and is transferred as an amount of charge to the MOS transistor 3 under the control of the timing generating circuit 1. The voltage is converted by the MOS transistor 3 and the resistor 4, sampled and held by the next stage MOS transistor 5, and supplied to the gate of the output stage MOS transistor. FIG. 2 shows the output timing waveform of FIG. 1. The standard level (1) C level) is
It is determined by the resistance division between the MOS transistor 6 and the resistor 7.

The strength of the optical signal is sent to the output as a change in the gate voltage of the MOS transistor. However, it has been established that the signal output from terminal 8 fluctuates with temperature changes. This may be due to the fact that the reference level (JJC level) drifts by several rTIV due to temperature changes, and the MO
S) This is thought to be due to the difference in the temperature coefficients of the on-resistances of Ranjistaro and resistor 7. Moreover, this number mv
This fluctuation is a value that cannot be ignored considering that the dark output of the CCD sensor is about 5 mV or lower.

As described above, the conventional CCD sensor has the drawback that a temperature drift of the I)C level occurs in the output stage circuit, which causes a non-negligible output fluctuation.

An object of the present invention is to provide a charge transfer device that eliminates variations in output due to temperature drift.

The charge transfer device of the present invention includes a second output circuit that receives charges transferred in a light-blocking state in parallel with a first output circuit that receives charges generated by light reception, and connects both output circuits. The present invention is characterized in that the output is input to a differential amplifier, and an output signal is obtained from the differential amplifier.

Hereinafter, one embodiment of the present invention will be fully explained using FIG. 3.4.

FIG. 3 is a circuit diagram of one embodiment of the present invention. 1'~7'
and 9' are the same as 1 to 7 and 9 of the conventional circuit, so a detailed explanation will be omitted. Reference numeral 20 denotes a dummy transfer section in which the light is cut off, and this is connected to the gate of the MOS transistor 10 forming the second output circuit. 10-14 are the same circuits as 3'-7'. 3'~
The actual output and dummy output from the first output circuit 7' are input to the differential amplifier 19 via resistors 15 to 19, respectively. The output end of this differential amplifier is connected to the output terminal 8'.

With this configuration, the temperature drift caused by the M(JS) transistor 13 and the resistor 7' is canceled by the temperature drift caused by the (J S ) transistor 13 and the resistor 14. That is, since the two output stages configured in the same shape have the same temperature drift, the output obtained from the differential amplifier becomes an output signal without temperature fluctuation. In addition, the reference level (D
C level) Changing the value of Sonomo does not pose any problem to external successors.

As explained above, since the output of the CCD sensor can be fully compensated for the temperature, there is an advantage that an accurate output voltage that does not depend on temperature changes can be obtained. Therefore, in a facsimile, it is possible to obtain a clear image even after one use in an environment where the temperature changes.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a conventional CCD sensor, Figure 2 is a timing waveform diagram of Figure 1, Figure 31) 1 is a circuit diagram of an embodiment of the present invention, and Figure 4 is a timing waveform diagram of Figure 31. It is a diagram. 1... Timing generation circuit, 1'... Timing generation circuit, 2... Light reception, transfer circuit, 2'...
・Light receiving, transfer circuit, 3...MOS) transistor, 3
'...MOS) transistor, 4...resistor, 4
' ・Resistance, 5, =-MOS) transistor, 5
′...[\I(JS transistor, 6...Mi
s) Ransistor, 6'...M (JSI-Ransistor, 7
...Resistance, 7' ...Resistance, 8...Output, 8'
...Output, 9... Gate voltage waveform of M (JS) transistor 5, 10 MUS transistor, 11
...Resistor, 12 ...M (JS) transistor, 13
...MOS) transistor, 14...resistance, 15
...Resistance, 16...Resistance, 17...Resistance, 18
Resistor, 19... Differential amplifier, 20... Dummy sensor, transfer circuit. Figure 3

Claims (1)

[Claims] A differential amplifier compares and outputs the outputs of a first output circuit that inputs charges generated by light reception and a second output circuit that inputs charges in a light-blocking state. charge transfer device.