| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a light emitting diode drive circuit, which is driven by a low voltage power source and does not much vary in the amount of light, irrespective of a change in temperature. SOLUTION: A resistor 3 for detecting a current is connected, in series with a transistor 1 for driving a light emitting diode 2 and a light emitting diode 2. The transistor 1 is driven by a transistor 5 driven by a drive voltage and is fed back, according to a voltage drop in the resistor 3 to control a light emitting diode drive current to keep the voltage drop in the resistor 3 at a constant value, whereby the transistor 1 is driven by a low power source voltage. Furthermore, a transistor 6 which is connected at the base to the transistor 5 is provided in the same package and a drive voltage is applied to the base of the transistor 6 to drive the transistors 5, 6, at the same time to make a temperature compensation for the transistor 5 by the transistor 6, whereby the amount of light emitted by the light emitting diode 2 is prevented from varying with the change in temperature.</p> |
