| 摘要 |
PURPOSE:To prevent a bipolar transistor (TR) from saturation and to prevent MOS TRs from malfunction by detecting the status that the base potential of the bipolar TR is higher than the collector potential and interrupting the bipolar TR. CONSTITUTION:The relation of levels of voltages V1, V3 is detected by TRs Q1, Q2, M5 constituting differential steps. The potential of voltages V2, V4 is turned to potential corresponding to three drops of forward drop voltage VBE of diodes D1, D2 from a power supply voltage VDD and the V1, V3 are turned to voltage dividing resistance based upon the ON resistance of MOS TRs M1, M2. When the VDD is dropped, the relation of levels of the V1 and V2 is reversed and the bipolar TRQ1 or Q2 is made saturated status. Therefore, the reach of the VDD close to VDD1 is detected so that the condition of V1>V2 is not formed, and the MOS TRs M5-M8 are turned off. |
