| 摘要 |
PURPOSE:To attain the detection of saturation of the collector current of an output transistor Tr by making use of a fact that a large base current flows apparently in comparison with a case where the collector voltage is high after the collector current of a Tr is saturated. CONSTITUTION:The collector current of an NPNTrQ7 increases when the collector current of an NPNTrQ6 is saturated with a current mirror circuit consisting of those NPN transistors TrQ5-Q7. Making use of this fact, the base of a PNPTrQ8 is connected to the collector of the TrQ7. While the emitter of the TrQ8 is connected to a power supply VCC. Then the saturation of the collector current of the TrQ6 is detected by the collector current of the TrQ8. When the collector current of the TrQ6 is saturated, the collector current of the TrQ7 is set at a higher level than the collector current of a TrQ4. The base current flows to the TrQ8 according to the current difference between both collector currents of the TrQ4 and Q7. Thus the TrQ8 is turned on..The collector currents produced by the ON/OFF operations of the TrQ7 are discriminated for detection of the saturation of the collector current of the TrQ6, i.e., an output current. |
