| 摘要 |
PURPOSE:To increase the response speed of a photodetecting element as well as the switching response of an output stage by using a potential setting circuit which sets the level of voltage applied to a photodetecting element as well as an impedance conversion element having low input impedance and high output impedance. CONSTITUTION:A transistor TRQ3 of an impedance converting circuit 14 has low input impedance and high output impedance owing to its base earthed type. Thus the load applied to a phototransistor TRQ1 is reduced to improve the response performance. In this case, the voltage VCE applied to the TRQ1 can be set freely by varying resistance R4 and R5 of a potential setting circuit 15. While a pnp type TRQ3 used to the circuit 14 consumes an extremely small amount of power. Furthermore, the switching response of an output TRQ2 is improved by facilitating the discharge of the carrier stored between the base and the emitter of the TRQ2 and with control of a resistance R6.
|
