| 摘要 |
PURPOSE:To prevent a transistor (TR) to be tested from breaking down even if abnormal oscillations are caused during a test by superposition a signal based upon a detected abnormal oscillation signal on a bias current limiting signal. CONSTITUTION:This device consists of a detecting circuit 8 which detects an abnormal oscillation signal when the TR 7 to be tested oscillates abnormally, a control circuit 10 which superposes the signal based upon the detected abnormal oscillation signal upon the bias current limiting signal, etc. When an output current to the TR 7 to be tested increases, the voltage drop across a resistance R4 increases, and consequently a TR 4 turns on to reduce the base bias of a TR 3, which turns off to limit the output current to the TR 7 to be tested. Then when the TR 7 to be tested oscillates abnormally, its signal is passed through a capacitor C1 and detected by a diode 9 to cause a voltage drop across the load resistance R7 of the diode 9. This voltage is applied to an operational amplifier 11 and superposed by the amplifier 11 so as to increase apparently the voltage drop across the resistance R4 which limits the output voltage of a power circuit eventually, thereby turning off the TR 3.
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