| 摘要 |
PURPOSE:To prevent a malfunction of a clock circuit due to piezo-voltage, by providing a diode for discharging the piezo-voltage, to an electric power amplifying part for driving a piezoelectric buzzer. CONSTITUTION:When a DC rectangular current signal is outputted from a buzzer signal output terminal of a clock circuit 1, a transistor 7 is turned on and off, DC sqaure wave voltage whose peak vlaue is equal to output voltage of a battery 5 is generated in an output terminal 23 of an integrated circuit 6, and by this voltage, a piezoelectric element 4 is driven. When a mechanical impulse is applied from the outside, piezo-voltage is generated between 2 electrodes of the piezoelectric element 4. Since a diode 9 or 10 works on this piezo- voltage, and generates an electric discharge path, collector voltage of the transistor 7 is clamped within a range of a value where 2 times of forward voltage of the diode was added to output voltage of the battery 4, and no abnormal operation is caused in the clock circuit 1. |
