| 摘要 |
<p>It is an object to prevent a light-emitting diode from keeping emitting a light when the input terminal is fixed to a high-level state due to a software or the like and to avoid various problems, such as battery exhaustion, destruction of the light-emitting diode and the like, from occurring in a PDA, a mobile telephone or the like. The object is accomplished by providing, in the state preceding a light-emitting element driver circuit (23) that drives a light-emitting diode (8) used for optical transmission, a highpass filter (21) that permits passage of the high frequency components of an optical transmission input signal composed of a pulse waveform, and a binarizer circuit (22) that binarizes and returns an output signal from the highpass filter (21) to the pulse waveform.</p> |
