| 摘要 |
PROBLEM TO BE SOLVED: To read/write data outputting an optimal modulated signal to each of IC cards, which can be accessed by respectively different amplitude transit modulated signals. SOLUTION: A modulation circuit 12 for a card reader/writer is provided with a driver DRV, a driving transistor Q composed of transistors Q1 and Q2 and a bias part 12B composed of resistors R1-R3. When a switching signal (b) is L, a voltage +V or 0 corresponding to H/L of a transmitting code (a) is impressed from the bias part to the gate of the transistor, the transistor is turned on/off and the modulated signal of modulation factor 100% is outputted from the transistor Q, to which the carrier signal is inputted. When the switching signal (b) is H level, on the other hand, a voltage +V or +(V-ΔV) corresponding to H/L of the transmitting code is impressed from the bias part to the gate of the transistor, and the modulated signal of modulation factor 100% is outputted. |
