| 摘要 |
<P>PROBLEM TO BE SOLVED: To prevent a voltage not lower than a breakdown voltage from being applied to an output transistor. Ž<P>SOLUTION: By a PWM signal, a pair of output transistors 16, 18 which are connected in series between a power source line and the ground is driven, and a push-pull current is outputted toward a speaker SP from the contact of both the output transistors 16, 18 via a coil L. A current-limiting resistor R1 is connected to the power source line as its one end, and a control transistor 24 is provided between the other end and the ground. Also, a comparator 26 compares the voltage of the power source line with a reference voltage, and turns on the control transistor 24 when the voltage of the power source line is higher than the reference voltage according to the comparison result. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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