| 摘要 |
PURPOSE:To improve the S/N by applying the class B or class AB push-pull drive to the 1st and 2nd light emitting elements respectively by a positive and negative half cycle signal so as to decrease the drive current of the 1st and 2nd light emitting elements. CONSTITUTION:A drive circuit 2 consists of the 1st amplifier circuit 6, a driver section 7 and the 1st and 2nd output transistors (TRs) 10, 11 in complementary connection via the 1st and 2nd emitter resistors 8, 9. The 1st and 2nd light emitting elements 3, 4 are connected to the collector of the TRs 10, 11. The operating point of the TRs 10, 11 is selected so that they are operated at the class B or AB push-pull operation. Thus, the elements 3, 4 are driven in push- pull by the position/negative half cycle signals to an input signal. Then the drive current of the elements 3, 4 is decreased and the S/N is improved.
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