Abstract: There is provided a surface-treated steel sheet (1) comprising: a tin-plated steel sheet (10) obtained by tin-plating a steel sheet (11); a phosphate compound layer (20) containing tin phosphate formed on the tin-plated steel sheet (10); and an aluminum-oxygen compound layer (30) on the phosphate compound layer (20), a main constituent of the aluminum-oxygen compound layer (30) being an aluminum-oxygen compound; wherein, when the 3d5/2 spectrum of tin in the aluminum-oxygen compound layer (30) is determined using an X-ray photoelectron spectroscopy, the ratio of the integration value of the profile derived from tin oxide to the integration value of the profile derived from tin phosphate (tin oxide/tin phosphate) is 6.9 or more.

Abstract: A switching circuit using first and second semiconductor devices each having a semiconductive substrate with a current path portion, first and second semiconductive regions forming a PN junction therebetween, the first region being capacitively coupled to the current path portion, a control electrode connected to the second region, a signal input terminal electrically connected to the first terminal of the first semiconductor device, an output terminal electrically connected to the second terminal of the first semiconductor device, means for connecting the control electrode of the first semiconductor device to the first terminal of the second semiconductor device, means for applying a bias voltage to the second terminal of the second semiconductor device, and switch means for selectively applying a bias voltage to the control electrode of said second semiconductor device. The switching circuit is operated with a signal applied to the control electrode of the second semiconductor device.