| 摘要 |
PURPOSE:To make it possible to correct the temperature characteristics of a light emitting element by a simple circuit constitution, by comparing the output current of a photocoupler with a reference current, and changing the reference current in correspondence with the temperature characteristics of the light emitting element in the photocoupler. CONSTITUTION:For example, when an ambient temperature becomes high, the light emitting efficiency of a light emitting diode D1 is decreased and an output current i1 is decreased. In a reference current supplying circuit 5, a forward current i2 flowing through a second diode D3 becomes small. Then a reference current i3, which is supplied to a current comparing circuit 3, becomes small. Therefore, second and third transistors Tr3 and Tr4 in a comparator part 3b are operated by the output current of a phototransistor Tr1, which is made small based on the reduction in the light emitting efficiency of the light emitting diode D1. When the temperature characteristics of the light emitting diode D1 are made to agree with that of a temperature correcting circuit 5b, the temperature characteristics of the light emitting diode D1 can be corrected. |
