| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a photoelectronic circuit having a wide dynamic range. SOLUTION: Light hνis introduced from a light emitting diode LED to an optical sensor 8 by feeding a driving current Id from a driving circuit 9 to the light emitting diode LED and light hν' modulated in the optical sensor 8 is received by a photodiode PD. A photocurrent Ip generated in the photodiode PD is compared with a reference current Iref by a current comparison circuit 10 and a comparison currentΔIp generated by the comparison is converted to a voltage signalΔVp by a current/voltage conversion circuit 13 to carry it through a low-pass filter 14. A direct current voltage componentΔVdc in a voltage signalΔVp ' outputted from the low pass filter 14 is extracted by a direct current component extraction circuit 15 and an average light receiving power on the light receiving surface of the photodiode PD is kept constant by returning the direct current voltage componentΔVdc to the driving circuit 9. A dynamic range is enlarged by comparing the photocurrent Ip with the reference current Iref .</p> |
