| 摘要 |
PURPOSE:To prevent oscillation by performing switching operation fast by composing the 2nd switch of an equivalent PNPN switch circuit in a comparator which has hysteresis characteristics through the switching of the 1st and 2nd switches. CONSTITUTION:When an input voltage E is higher than a reference voltage Vt1 obtained through the voltage division of resistances R11 and R12, a transistor TR11 turns on, a TR12 turns off, and a TR17, therefore, turns off, so that any voltage is developed at an output terminal. When the voltage drops below the voltage Vt1, the TR11 turns off and the TR12 also turns off. This inversion is performed rapidly because a TR13 constituting an equivalent PNPN switch circuit also operates in cooperation, and a resistance R13 is inserted in parallel to the R11, so that the reference voltage applied to the base of the TR12 rises up to a Vt2. When the voltage E rises above the voltage Vt2, the TR11 turns on, and the TRs 12, 13 and 17 turn off to make the reference voltage drop down to the Vt1, ceasing the output voltage. The switching of the reference voltage is performed simultaneously with the on-off operation of the TR12, so oscillation never occurs. |
