| 摘要 |
PURPOSE:To prevent the destruction of an electronic circuit due to the abnormal state of the electronic circuit and an excessive current, by providing a first transistor, which supplies power to the electronic circuit, a resistor, which detects the excessive current, and a second transistor, which isolates the first transistor at the time of the excessive current. CONSTITUTION:Transistor 8 supplies power to a terminal 2. A current source 11 is set so that a voltage at a terminal 2 does not become lower than the voltage of a power source 7 to a large extent and the device is operated in a saturated region. When the excessive power source current flows at an abnormal time, the potential difference across a detecting resistor 9 is increased, and a cut-off transistor 10 is operated. The transistor 10 not only interrupts the power supply transistor 8 and protects a electronic circuit 1 but also prevents the damage of the power source 7. |
