A semiconductor integrated circuit device and a contactless electronic device are provided with a power supply circuit producing a stable smooth voltage with high efficiency for stable operation of an inner circuit. An AC voltage is applied to first and second input terminals and a rectification transistor having drain (or collector) connected to second input terminal and gate (or base) and drain (or collector) connected to each other through resistor supplies a rectified current between the first and second input terminals. The first voltage detection means produces control voltage so that the rectified voltage obtained on the source (or emitter) side of the first rectification transistor is equal to the predetermined reference voltage. The first voltage controlled current source can produce current in accordance with the control voltage and supply the current to the first resistor means. Such power supply circuit is mounted in the contactless electronic device.