| 摘要 |
In an IC card, even in the case where an undershoot or an overshoot which occurs at the time of an amplitude change by communication data is large, the amplitude change is accurately detected. A semiconductor integrated circuit device B2 has antenna terminals LA and LB, a power supply circuit B3 for generating power supply voltage from an alternating-current (AC) signal supplied to the antenna terminals, and a receiver circuit B5 for demodulating an information signal which is superimposed on the AC signal. The receiver circuit B5 includes a rectifier circuit B9, a filter circuit B10, a capacitor C1, an amplifier A1, a feedback path B11, a switch circuit SW1, a binarizing circuit B12, and a control circuit B13. An output signal S3 of the amplifier A1 is transmitted to an inverting input terminal - of A1 via B11 and SW1, and the switch circuit SW1 is controlled by an output signal SC1 of the control circuit B13. In a lapse period of predetermined time T1 since level changes X and Y of an output signal SR of the binarizing circuit B12, the switch circuit SW1 is controlled to an off state by the output signal SC1 of the control circuit B13.
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