| 摘要 |
PURPOSE:To obtain a voltage-range detection circuit of simple constitution with low part cost, by making Zener diodes and transistors, connected to them at their bases, correspond to a required number of limit voltage. CONSTITUTION:A required number of limit voltages Va, Vb and Vc are made to correspond to Zener voltages of Zener diodes Za, Zb and Zc to obtain the relation of Va<Vb<Vc; with input voltage Vi less than Va, Zener diodes are all OFF, transistors Ta, Tb and Tc are all OFF, and outputs A, B and C are ''H''. With the relation of Va<Vi<Vb, Za and Ta are both ON and A is ''L''. At the time of Vb< Vi<Vc, Zb and Tb are both ON and diode Dab makes short between the base and emitter of Ta to turn Ta OFF, so that only Tb will ON with B ''L''. Similarly, at the time of Vc<Vi, only Tc is ON and C is ''L'', thereby making it possible to detect the voltage range. |
