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 with a sensor section for converting
X-rays to an amount of charge according to the amount of X-rays, a charge collecting
electrode for storing the charge generated, a read gate for transferring the stored
charge to an external read amplifier and a MIS diode using a TFT. A clamp signal
is applied to one end of the MIS diode. The read gate and MIS diode are formed
in the same manufacturing process. Since the amount of charge stored in the charge
collecting electrode is clamped to the amount of charge corresponding to the clamp
signal voltage by the MIS diode, the read gate is not destroyed even with excessive
X-ray irradiation. Furthermore, instead of the MIS diode, a cutoff voltage control
circuit and a cutoff gate using a TFT connected to the cutoff voltage control circuit
are provided. When the output of the charge storage capacitor exceeds a cutoff
voltage, the cutoff gate interrupts the inflow of charge to the charge storage
capacitor to suppress further increase of output, thus preventing the read gate
from being destroyed.
