This simple circuit can help me a lot in many cases. He can test the quality of the triode. In the circuit, between BC as low as 40 ohms or between BE, he can check the power output in the amplifier circuit. Transistor.
The circuit principle is as follows:
The 555 timer (IC1) operates as a 12 Hz oscillator and the 3-pin output drives a 4027 (IC2) bistable circuit. After dividing by 2 and outputting at 14,15 feet, the output is connected to LED1 and LED2 through current limiting resistor R3. The two LEDs have been arranged, so when the transistors of different polarity are connected to the circuit, only one LED emits light, when there is no triode When entering, the two LEDs will alternately flash. 14,15 pin output through the voltage divider resistor R4 is connected to the B pole of the measured triode in R5. When a good triode is connected, the triode is turned on, creating a path for one of the two LEDs, if a good NPN When the triode is connected, LED1 will flash. If PNP transistor is connected, LED2 will flash. If an open-circuited triode is connected, the two LEDs flash in turn. If a short-circuited triode is connected, neither LED blinks.
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