Patent ID: 6831378
Filing Date: 2004-12-14
Classification: G06K

Abstract:
A contactless electric device comprising:an antenna to receive a signal and electric power; a power supply circuit to produce an internal voltage from the electric power received by said antenna; and an inner circuit operated by said internal voltage produced by said power supply circuit to process the signal received by said antenna, wherein said power supply circuit includes: first and second input terminals connected with said antenna; first and second output terminals connected with said inner circuit; a first rectification transistor having a source-drain path or a collector-emitter path connected between said second input terminal and said second output terminal; a first resistor connected between said second input terminal and a gate or a base of said first rectification transistor; a second rectification transistor having a source-drain path or a collector-emitter path connected between said first input terminal and said second output terminal; a second resistor connected between said first input terminal and a gate or a base of said second rectification transistor; a voltage controlled current source to produce a current in accordance with a control voltage to supply said first and second resistors; and a voltage detection circuit to produce the control voltage in accordance with a voltage between said first and second output terminals.