Kabushiki Kaisha Toshiba

Tatsuya Yoshie

Tatsuo Sakaue

Shin-ichi Imai

In a charge transfer device, a voltage generating cirucit generates a voltage amounting to a potential lower by '.alpha.' (.alpha.: a predetermined potential) than a potential formed under a reset gate electrode when stored charges of a floating diffusion region are discharged into a drain region. A voltage step-up circuit steps up a predetermined voltage and supplies the stepped-up voltage as a reset voltage to the drain region. A comparison/control circuit generates an error voltage amounting to a difference between the output voltage of the voltage generating circuit and the stepped-up voltage, and controls the voltage step-up operation by the step-up circuit according to the error voltage. With the structure of the device, the stepped-up voltage from the voltage step-up circuit, which is supplied as a reset voltage to the drain region, is controlled according to the process parameter variations. The result is that the reset voltage well follows up the process parameter variations, the dynamic range of the output signal is always kept wide, and the output signal of good linearity and good S/N performance can be obtained.

Charge transfer device with reset voltage generating circuit

A charge transfer device includes a charge transfer unit having a plurality of charge transfer cells for transferring a signal charge by the charge transfer cells, a first floating diffusion region adjacent to the charge transfer unit for storing the signal charge transferred by the charge transfer cells, first control switch means driven by a first reset pulse, and a first reset power source connected to the first floating diffusion region through the first control switch means. The charge transfer device further includes second control switch means driven by a second reset pulse, a second reset power source connected to the second floating diffusion region through the second control switch means, a capacitor coupling the first floating diffusion region to the second floating diffusion region, and detector means for detecting a potential change of the second floating diffusion region to output the potential change as an output signal corresponding to the signal charge. MOS transistors may be employed for the control switches in the output stages. This novel charge transfer device can provide a sufficiently broad output dynamic range and an output signal having a good linearity even when a lower voltage is used for the power supply voltage.

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Yokohama, Japan

Tatsuya Yoshie