Discrimination of polarity and quality of transistor pins 2

(2) Discrimination between emitter and collector electrodes

After identifying the base and transistor, determine the emitter and collector. The method is: taking an NPN transistor as an example, assuming that one of the other two pins is the collector,diode connect the black probe (corresponding to the positive terminal of the battery in the meter) to this pin, connect the red probe to the assumed emitter, and cross a resistor of 100 kQ or more between the assumed collector and the measured base (often hold b and c in your hand, replace them with human resistance, but do not touch the two pins), and record the resistance reading at this time; Set the assumed collector as the emitter and the original emitter as the collector, diodeand repeat the test reading. The assumption that the resistance value is smaller (with a larger deflection angle) in the two readings is correct, with the black probe connected to the collector pin and the remaining pin being the emitter. If it is a PNP tube, swap the probes and use the above method to determine.diode

(3) Identification of transistor performance

① Judging the quality of a transistor: During testing, use a multimeter to test the forward and reverse resistance of the emitter and collector junctions separately. If it is within the normal range, it indicates that the transistor is fine; otherwise, it is damaged.diode

② Determination of Penetrating Current ICEO: Use a multimeter R × 100 (Q) or R × 1k (Q) to measure the collector emitter resistance (for NPN transistors, connect the black probe to the collector and the red probe to the emitter). The larger the value, the smaller the ICEO. Generally, silicon tubes should be greater than several megaohms, while germanium tubes should be greater than several kiloohms.

When the measured resistance value is infinite, it indicates that there is a broken wire inside the tube; When the measured resistance value approaches zero, it indicates that the tube has been broken down; Sometimes the resistance value keeps decreasing, indicating unstable performance of the pipe.diode