| 摘要 |
PURPOSE:To obtain an excellent APC characteristic independently of the P-I characteristic and the temperature range of a light emitting element by providing a variable resistance element in parallel with a light emitting element of a laser diode or in parallel therewith via a resistor, bringing the resistance to a high resistance at a high temperature and to a low resistance at a low temperature. CONSTITUTION:A variable resistance element 9 is connected in parallel with a light emitting element LD 3 and its resistance varies with a control signal. A temperature sensor 10 outputs a control signal to bring a resistance of the variable resistance element 9 to a high resistance at a high temperature and to a low resistance at a low temperature to the variable resistance element 9. A resistance of 300ohms is obtained at the low resistance state and a resistance of 10kohms is obtained at the high resistance state in the variable resistance element 9 by employing a FET 11 and using its drain and source at terminals as the resistive element and using its gate as a variable control terminal. The temperature sensor 10 consists of a circuit network comprising of a resistor 12, a thermister 13 and a power supply 14. An output current of a current amplifier 6 is divided to an LD 3 and the variable resistance element 9 at each temperature and the output current is increased more than the case of connection of an LD single body and a current amplification factor beta is increased sufficiently at each temperature and the excellent APC characteristic is attained. |
