Patent ID: 8781537

Claim:
A semiconductor integrated circuit comprising: a pair of antenna terminals connectable with an antenna; a rectifier operable to rectify a radio frequency signal supplied through the pair of antenna terminals thereby to output a direct-current voltage to an inside source line; a source-voltage terminal for supply of a source voltage from outside; a shunt regulator including a pull-down transistor connected between the inside source line and a ground, and passing a pull-down current through the pull-down transistor in response to a rise of a voltage of the inside source line to or above a first set voltage; a series regulator including a pull-up transistor connected between the source-voltage terminal and inside source line, and passing a pull-up current through the pull-up transistor in response to a fall of the voltage of the inside source line to or below a second set voltage; and a detector connected with the pair of antenna terminals, wherein the detector controls a voltage level of the first set voltage into a level higher than a voltage level of the second set voltage in case that the shunt and series regulators work in parallel, wherein the shunt regulator further includes a first voltage divider connected between the inside source line and ground, and a first operational amplifier operable to control an input terminal of the pull-down transistor according to a divided voltage output from the first voltage divider and a first reference voltage, and wherein the series regulator further includes a second voltage divider connected between the inside source line and the ground, and a second operational amplifier operable to control an input terminal of the pull-up transistor according to a divided voltage output from the second voltage divider and a second reference voltage.