| 摘要 |
<p>PURPOSE:To prevent an LED from decreasing in output even if it increases in temperature by a method wherein a circuit structure which compensates the change of the LED in output with temperature change is provided. CONSTITUTION:An NPN type transistor 2 is connected at its collector to a power supply through a protective resistor 10 and at its emitter to the anode of an LED 1. The cathode of the LED is connected to a resistor 3, whose one end is connected to the cathode of the LED 1 and other end grounded, A first and a second potential dividing resistors 4 and 5, whose ends are connected to the anode and the cathode of the LED 1, respectively and other ends are connected to each other, and an operational amplifier 6, whose non-reverse input terminal, reverse input terminal, and output terminal are connected to a low voltage power supply (voltage Vconst), a joint between the resistors 4 and 5, and the base of the transistor 2, are provided. That is, an LED is provided with a circuit which compensates the change of the LED in output with temperature change. By this setup, the LED 1 can thus be prevented from decreasing in optical output even if it increases in temperature.</p> |
