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A simple integrated power supply circuit in ESFI-SOS technology with only one external capacitor is presented. The circuit, which can directly be applied to 110 V AC line voltages, comprises a bridge rectifier, a `lambda'-type current switch, and a series regulator with overload protection. Because of the relatively small area consumption (6 mm/SUP 2/) the circuit to be supplied can easily be integrated on the same chip. Experimental results show a DC output power of about 100 mW (10 V/10 mA). Due to the lambda-type current switching high efficiencies of more than 30 percent are achieved. With some additional device modifications to increase breakdown voltage it should be possible to operate such circuits also with 220 V AC line voltages.