Description
Following is a sample of the information contained on this CD: CROSS-REFERENCE TO RELATED APPLICATION This application claims the priority benefit of Taiwan application Ser. No. 94123192, filed on Jul. 8, 2005. All disclosure of the Taiwan application is incorporated herein by reference. BACKGROUND OF THE INVENTION 1. Field of Invention The present invention relates to a power output device, and more particularly, to a power output device with protection function for short circuit and overload. 2. Description of the Related Art A conventional power output device usually uses a transistor or a plurality of transistors to form a bridged output stage for amplifying a signal and outputting the amplified signal to a load. An inadvertent operation, however, may cause an abnormally large current flowing through the transistors and thus damaging the transistors. For example, load is in short circuit, and the output terminal is short to ground or to a voltage source, all such foregoing conditions may easily damage the whole circuit and cause danger. For the reason to prevent the power output device being out of order due to the aforementioned abnormal operation, and thereby improve reliability of circuit, a protection circuit for short circuit and overload is designed to protect the power output device. FIG. 1 is a conventional power output device with a protection circuit for short circuit and overload. Referring to FIG. 1, the power output device comprises an input control unit 11 for receiving a signal, a driving circuit 12 for receiving the output signal from the input control unit 11, a power output unit 13 driven by the driving circuit 12 for outputting an amplified signal to a load 10, a resistor 14 connected in series with the load 10, a reference voltage source 15 and a comparator 16. The power output unit 13 can be constructed by a transistor. The output current from the transistor flows through the load 10 and the resistor 14, on which a
