HIGH SPEED OPTICAL TRANSMISSION CIRCUIT

摘要

PURPOSE:To obtain high speed optical transmission by supplying a current pulse to a light emitting element so as to discharge the charge stored in a parasitic junction capacitance thereby reducing a trailing time of an optical output waveform. CONSTITUTION:A digital signal fed to an input terminal 11 is applied to a transmission circuit 12, in which voltage current conversion is executed. An output current signal is fed to a cathode of a light emitting diode 13 and a power supply voltage Vcc is applied to the anode. The light emitting diode 13 has a parasitic junction capacitance 14. On the other hand, the digital signal fed to the input terminal 11 is fed to a pulse signal generating circuit 15. The digital signal is inverted by an inverter 16 and differentiated by a differentiation capacitor 17 and the result is fed to a circuit 18 generating a pulse current signal synchronously with the trailing edge of the digital signal. An output of the circuit 18 is fed to a current mirror circuit 19 supplying the pulse current output to the cathode of the light emitting diode 13 and the charge of the junction capacitance 14 of the light emitting diode 13 is discharged to reduce the trailing time.