| 摘要 |
PURPOSE:To extend the range of incident photo strength to keep the oscillation, by providing a Zener diode and a capacitor between the negative power supply of the photo oscillation circuit consisting of NPN transistor Tr, PNPTr and photo diode, and NPNTr. CONSTITUTION:When incident light to the photo diode 4 is increased and the voltage drop consisting of the current in NPNTr1 and the resistor 8 is greater than the zener voltage of the Zener diode 5, back bias voltage is made between the emitter and the base of Tr1 to interrupt the collector current of Tr1. Thus, the voltage drop of the resistor 7 is avoided and the base potential of PNPTr2 is of the same potential as the positive electrode of the power supply 3, but the emitter of Tr2 is at lower potential than the base with the charging of the capacitor C6 and Tr2 does not turn on until C6 is finished for discharge with the photo current of the diode 4. Further, Tr1 does not turn on until the voltage across C9 is less than the Zener voltage. Tr1 and 2 are turned on, and this is repeated to cause oscillation state. The stop of oscillation is not caused even with strong incident light. |
