| 摘要 |
In order to prevent destruction of a read gate by excessive storage of charge without any addition or change to the manufacturing process, the array type X-ray detection apparatus using a direct conversion system, which directly converts irradiation X-rays to charge, provides each pixel cell 30 with a sensor section for converting X-rays to an amount of charge according to the amount of X-rays, a charge collecting electrode 3 for storing the charge generated, a read gate 6 for transferring the stored charge to an external read amplifier and a MIS diode 10 using a TFT. A clamp signal is applied to one end of the MIS diode 10. The read gate 6 and MIS diode 10 are formed in the same manufacturing process. Since the amount of charge stored in the charge collecting electrode 3 is clamped to the amount of charge corresponding to the clamp signal voltage by the MIS diode 10, the read gate is not destroyed even with excessive X-ray irradiation. Furthermore, instead of the MIS diode 10, a cutoff voltage control circuit 44 and a cutoff gate 41 using a TFT connected to the cutoff voltage control circuit 44 are provided. When the output of the charge storage capacitor 42 exceeds a cutoff voltage, the cutoff gate 41 interrupts the inflow of charge to the charge storage capacitor to suppress further increase of output, thus preventing the read gate 6 from being destroyed.
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