| 摘要 |
PURPOSE:To attain the high speed switching by the unsaturating operation of a transistor (TR) and to use an emitter resistor as a protection resistor of a light emitting diode by using the emitter load resistor as a switching resistor of the light emission diode. CONSTITUTION:A light emission diode 2 is connected between an emitter and a collector of the TR 1 provided with the emitter load resistor 3. Then the effect of the Miller's effect due to the collector-base capacitance is reduced to prevent the reduction if the amplification factor at high frequencies. Further, the TR circuit is used at the unsaturated switching operation and the light- forward voltage characteristic of the light emission diode itself is used, then the high speed switching of the light switching is attained. Further, the emitter resistor 3 is used as a protection resistor of the light emission diode 2.
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