| 摘要 |
PURPOSE:To form a negative feedback loop having a high speed and high gain by providing a voltage/current converter between a voltage input signal source and a signal adder, and adding the detected current of a photodetector directly as voltage/current converter output. CONSTITUTION:A voltage/current converter 26 is provided between a voltage input signal source 27 and a signal adder 28 to produce out of a loop, thereby operating all the currents in the loop. A current amplifier is not provided between the output of a photodetector 22 and the adder 28, and the detected current of the detector 22 is added to the output of the converter 26. Thus, an element having frequency characteristic is not provided on a feedback path from a semiconductor light emitting element 21 to the adder 28, thereby improving the frequency characteristic of the closed loop. Further, a current amplifier 29 provided between the adder 28 and the element 21 is reduced to an input impedance current amplifier. Thus, unnecessary signal caused by the voltage signal is not generated in the loop to cause an erroneous operation. |
