| 摘要 |
PURPOSE:To contrive stable driving of LED by constant current by a method wherein plural switch circuits, which are furnished with one input terminal respectively and plural light emitting elements, whose output of respective current mirror circuit's output element is regarded as input, are provided. CONSTITUTION:Each switch circuit 10 is connected with reference electric current 8 commonly through a FET7, and respective circuit is wound in series between output at an electric power source and ground. Electric current, which is absorbed from reference current circuit 8, makes constant voltage drop be tween the output of the electric source 2 and the gate terminal G of the FET7 and then the gate terminal G of the FET7 is subjected to run through to a gate terminal G of a FET11 by means that a signal terminal 1 drives switch circuit 10. When absolute value of a resistance 9 is equal to absolute value of a resistance 12 and the FET7 characteristic is equal to the FET11 characteris tic, a LEP5 is emitted and a exposed drum 6 is exposed while the same value current as current absorbed from reference electric circuit is flowed to the LED5. Thereby, output voltage value's variation of voltage 2 and forward voltage's dispersion of the LED5 are eliminated, accordingly dispersion of elec tric current flowed to the LED5 can be reduced. |
