| 摘要 |
PURPOSE:To improve the symmetry of optical pulses generated from a light emitting element by a method wherein a constant current induced by a third transistor Tr is made to increase at the rise of an operating current of the light emitting element and to increase at the fall of the operating current at a rate larger than that at the rise. CONSTITUTION:A current which is made to flow according to binary signals inputted into a light emitting element 13 which is connected in series to a first transistor Tr 12 of a light emitting element drive circuit is switched. A second Tr 14 is connected to the first Tr 12 in parallel and executes a switching operation contrary to the Tr 12. A third Tr 15 is connected to the Trs 12 and 14 in series, and a constant current is made to flow through the Trs 12 and 14 connected in parallel through the Tr 15. Then, binary signals, which enable a current to flow through the element 13, are generated from a differential signal generating circuit and supplied to a first and second pulse generating circuit, 18 and 19. The current of the Tr 14 is made to increase at the rise of operating current of the element 13 through the circuits 18 and 19 and to increase at the fall of the operating current at a rate larger than that at the rise. |
