| 摘要 |
<p>PURPOSE:To improve response characteristic of switching of a light emitting means by switching a differential amplification circuit based on a control input signal and by forward biasing a light emitting means by a bias means in accordance with variation of output of the circuit. CONSTITUTION:In the case a control input signal Vin is L level, an H signal is output from an output terminal 3a of a logical circuit 3 in a differential amplification circuit 2 and a base electric potential of a switching transistor SW-Tr 4 becomes H level. An L signal is output from an output terminal 3b of the logical circuit 3, a base electric potential of an SW-Tr 5 becomes L level, the SW-Tr 4 turns 'on', the SW-Tr 5 turns 'off' and a light emitting diode 1 turns 'off'. Meanwhile, when the control input signal Vin changes to H level, the light emitting diode 1 turns 'on' to irradiate with a photo signal. In the process, the light emitting diode 1 is forward biased by a bias means 10 using a p-n-p transistor 15 to realize a rapid switching.</p> |
