Patent ID: 8198983

Claim:
A semiconductor integrated circuit, comprising: first and second antenna terminals for connection to an antenna; a power supply circuit for performing rectification of signals between the first and second antenna terminals and voltage control; and a load modulator for performing modulation of the signals between the first and second antenna terminals, wherein, in a current-voltage characteristic between the first and second antenna terminals in a region where an output voltage of the power supply circuit reaches a predetermined voltage and a voltage suppression operation works, a voltage change slope in a first current region is larger than a voltage change slope in a second current region having a higher current that of the first current region, wherein the power supply circuit has a first voltage controlled circuit and a first voltage detector, wherein the first voltage controlled circuit is provided with a first input terminal and a first output terminal, wherein between the first input terminal and the first output terminal, a first MOS transistor having a first resistor and a second resistor connected in series between a gate and a drain thereof is connected, wherein between a connecting point of the first resistor and the second resistor and a ground terminal, a second MOS transistor whose gate is connected to the first input terminal and a third MOS transistor are connected in series, wherein between the gate of the first MOS transistor and the ground terminal, a fourth MOS transistor whose gate is connected to the first input terminal, a current limiter, and a fifth MOS transistor are connected in series, wherein the gates of the third MOS transistor and the fifth MOS transistor are connected to an output terminal of the first voltage detector, wherein the current limiter controls current flowing between a drain and a source of the fifth MOS transistor, thereby controlling voltage which can be generated in the second resistor, wherein a first input terminal of the first voltage controlled circuit is connected to the first antenna terminal, wherein a first output terminal of the first voltage controlled circuit is connected to a power supply terminal, and wherein the first voltage detector outputs a voltage corresponding to a power supply voltage generated between the power supply terminal and the ground terminal.