Use headphones to judge transistors

1) To determine the PNP type and NPN type, measure the base, connect the black test lead (negative lead of the power supply) to pin 2 or 3 of v, and connect the red test lead (positive lead of the power supply) to pin 1. If in one of the three tests, when the black test lead touches the other two poles, the earphone BE can make a loud "click" sound, then the pin 1 that the red test lead touches this time is the base, and the tube is NPN type, such as As shown in Figure b. If the black test lead touches pin 3, and the earphones make a loud "click" sound when the red test lead touches pin 1 or 2, then the pin 3 touched by the black test lead is the base, and the tube is a PNP type. , as shown in Figure C. 2) Determine the emitter E and collector C. For PNP transistors, after knowing the base B, you can connect the black test lead to the base B and the red test lead to touch the other two poles respectively. In the two touches, the sound from the earphone BE is different in size, whichever one makes the louder sound shall prevail. At this time, the pin touched by the red test pen is the emitter E, and the remaining pin is Collector c. For low-frequency PNP transistors, you can insert a 100k12 resistor in the lead of the red test lead as shown in Figure d, touch the other two electrodes with the red and black test leads at the same time, pay attention to the sound volume emitted by the headphones, and then put the red test lead , exchange the black test lead, and then touch the two poles at the same time, the headset will also make a sound. Compare the two sounds, whichever one is louder shall prevail. At this time, the transistor pin that is in contact with the red test lead will It is the emitter E, and the other pin is the collector C.