| 摘要 |
PROBLEM TO BE SOLVED: To maintain always the current image magnification of a light- receiving device at a desired current image magnification by a method wherein a potential difference, which is changed according to a temperature change in a photodetector, is generated via a load resistor connected between a first transistor circuit and a second transistor circuit and a bias voltage to respond to the potential difference is generated to feed the bias voltage to the photodetector. SOLUTION: An amplifier 81 is formed of transistors Q1 and Q2 which are used as first transistor circuits, a temperature detection part 82 is formed of a transistor Q3 which is used as a second transistor circuit, and a potential difference ΔVBE which is changed according to a temperature change in a photodetector 42 is generated via a load resistor RE connected between an emitter voltage VE1 of the transistor Q1 of the amplifier 81 and an emitter voltage VE1 of the transistor Q3 of the detection part 82. A bias voltage VB1 to respond to the potential difference ΔVBE is generated to feed the bias voltage VB1 to the photodetector 42. As a result, a light-receiving device can always obtain a desired current image magnification regardless of the temperature change in the photodetector 42. |
