For the integration of an npn bipolar transistor with a hetero bipolar transistor, a placeholder layer is generated in a base region of the hetero bipolar transistor after structuring a collector structure for both types of transistors, wherein the placeholder layer is not present in a base region of the bipolar transistor. The apparatus further includes a near infrared ray source that provided between the X-ray source and the pressing panel and arranged in a two-dimensional shape in alignment with the pressing panel, and that is movable between a first position in close contact with the pressing panel and a second position outside an X-ray image capture region. Drift of a circuit providing such an inductor current estimation is preferably avoided by adjusting control duty cycle or slew rate of the positive-going ramp portion of the estimated inductor current triangular waveform. The insulation layer is disposed on the gate layer.