| 摘要 |
<p>PURPOSE:To reduce the electric current consumption of the light emitting circuit of the title circuit by comparing the output of a low-pass filter with the output of a reference power source by means of a differential amplifier and outputting the output of a gain circuit to an output terminal by amplifying the output of the gain circuit in accordance with the output variation of the low-pass filter so that a fixed voltage can be outputted to the output terminal. CONSTITUTION:When a driving power source 11 is turned on, light is outputted from a light emitting element 1 to an optical sensor 3 through an optical fiber 2 and an output corresponding to the optical signal of the sensor 3 is outputted to a light receiving element. An electromotive current from the light receiving element is outputted to a low-pass filter 17 through a gain circuit 24. While the voltage inputted to the filter 17 contains a DC component indicating a light quantity and an AC component modulated by the signal impressed upon the sensor 3, the filter 17 detects the DC component only and outputs the DC component to an automatic gain control circuit 20. When the light emitting or light receiving element normally operates without receiving any influence from the ambient temperature, the output of the filter 17 becomes equal to the output of a reference power source 21 and the base current to be outputted from the circuit 20 becomes constant. As a result, the voltage outputted to an output terminal 7 becomes constant.</p> |
