Heat radiation increased and over current load avoided small sized power supply

The electronic device for processing an electronic signal and outputting an electronic signal undergone the process of rectification is characterized by that the drain electrode of a rectification integrated wafer (MOSFET) is welded together with a copper cover or a copper strip, and covered with it, and the copper cover or copper strip also can be formed into the drain electrode of MOSFET so as to increase radiating area, and can prevent the excessive drain current from conducting to PCB board and prevent the electroni elements on the PCB board from being burnt out by excessive current, at the same time the circuit package volume also can be reduced.