| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a constant current circuit, along with a light-emitting diode driving device, which outputs precise constant currents independent of the voltage of an output terminal with a simple circuit, and reduces the voltage of the output terminal without degrading output precision of the constant current, for significantly reduced power consumption. <P>SOLUTION: The constant current circuit comprises an NMOS transistor M1 which acts as a current source supplying a current corresponding to the control signal inputted in a gate, an NMOS transistor M2 which supplies a current corresponding to the control signal inputted in the gate to an external load 10, a voltage regulating circuit 3 which controls a drain voltage of the NMOS transistor M1 so as to be the drain voltage of the NMOS transistor M2, a current detecting circuit 4 which detects a current value that flows the NMOS transistor M1, and a control circuit 5 which controls gate voltages of the NMOS transistors M1 and M2 so that the current flowing through the NMOS transistor M1 comes to be a specified value according to the detection result of the current detecting circuit 4. <P>COPYRIGHT: (C)2008,JPO&INPIT</p> |
