| 摘要 |
PURPOSE:To execute optimum light modulation irrespective of the number of channels of a multiple signal by installing a circuit to detect the peak level of the multiple signal at the output side of a gain variable amplification circuit, and controlling the gain variable amplification circuit by generating control voltage by comparing the peak level with reference voltage. CONSTITUTION:The peak detection circuit 2 detects the peak level of the multiple signal the gain variable amplification circuit 1 outputs, and outputs voltage V2 showing the peak level. A differential amplification circuit 3 receives the reference voltage V1 a reference voltage generation circuit 4 outputs and the voltage V2 the peak detection circuit 2 outputs, and sends their difference as the control voltage V3 to the gain variable amplification circuit 1. The gain variable amplification circuit 1 receives the inputted multiple signal S1, and sends the multiple signal S2 of the constant peak level to a light modulation circuit 5 by controlling its gain according to the control voltage V3. The light modulation circuit 5 drives a light emitting element 6 according to the multiple signal S2, and generates a light signal. Thus, a total modulation degree in the light emitting element 6 can always be controlled so as to be constant. |
