| 摘要 |
PURPOSE: To shorten the burst response time by amplifying the difference between a binary data signal and the output signal of a light receiving element thus driving light emitting element. CONSTITUTION: The binary data signal applied to an input terminal 1 is impressed to the base of a transistor TR 4 through a buffer circuit 2. When the binary data signal becomes high, the TR 4 is turned on, and the output current of a constant current source 3 flows to a light emitting element 6, and the element 6 emits light. Then, a current flows to a light receiving element 7, and the output current of the element 7 is converted to a voltage by a resistance 8, and it is amplified by an amplifier 9 and is impressed to the base of a TR 5. If the degree of amplification of the amplifier 9 is so set that the TR 5 starts conduction when the optical output of the element 6 reaches a prescribed value, the TR 5 is made to conduct and a part of the output current of the current source 3 flows to the TR 5 when the optical output of the element 5 exceeds the prescribed value. Thus, the current flowing to the element 6 is kept at a certain value because being limited, and the optical output of the element 6 is controlled each time when the binary data signal becomes high. |
