| 摘要 |
PURPOSE:To reproduce a signal in an medium sound zone having a flatness throughout a wide band by selecting a winding ratio of the primary side and the secondary side of a transformer to 1:4 or above and setting the impedance of the secondary coil to be equal to the impedance of a piezoelectric speaker or a slightly lower value. CONSTITUTION:The winding ratio of the primary (output transistor side) and the secondary (piezoelectric speaker side) coils 12, 13 of a step up transformer driving a piezoelectric speaker 7 using a piezoelectric buzzer element 4 is selected to be 1:4 or above. Further, the impedance of the secondary coil 13 is selected to be equal to that of the piezoelectric speaker or slightly lower value than that. On such a magnetic core 10, the primary coil 12 and the secon dary coil 13 are wound. In such a case, since the connecting factor of the pri mary coil 12 and the secondary coil 13 is preferably large, both the coils 12 and 13, as shown by the figure, may be wound in a what is called lap winding. |
