| 摘要 |
PROBLEM TO BE SOLVED: To provide a light emitting element drive circuit capable of rapidly falling an optical output wave form with suppressing ringing at start thereof. SOLUTION: The drive circuit comprises a plurality of parallel connected differential circuits for feeding a semiconductor element with a drive current, a plurality of current sources for feeding two transistors constituting the differential circuit with a specified constant current, first switching transistors connected in series to inputs of the transistor so as to be set to an ON-state at start of an optical output waveform, first resistors set to resistance values enough for suppressing the ringing at the start of the output waveform, second switching transistors connected in parallel to the first switching transistors and the first resistors so as to be set to an OFF-state at the start of the output waveform, and second resistors set to resistance values so as to quickly drop the output waveform.
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