How to distinguish PNP type and NPN type triodes?

Semiconductor triode, also known as crystal triode, can be said to be the most important device in electronic circuits. Its main functions are current amplification and switching. The triode has three electrodes as the name suggests. The diode is made of a PN structure, while the triode is made of two PN structures. The common electrode becomes the base of the triode (represented by the letter B - B is taken from the English Base, basic and basic). The other two electrodes are respectively called the collector (represented by the letter C - C is taken from the English Collector, collection) and the emitter (represented by the letter E - E is taken from the English Emitter, emission).

The main parameters of triode are penetration current and amplification. The smaller the penetration current Iceo is, the better the stability of the triode is. Magnification β Generally from tens to hundreds, which should be selected according to the needs of the circuit.

Judge according to the shape of triode

1. Generally speaking, the shell of PNP type triode is much higher than that of NPN type. In addition, there is a prominent mark on the shell of NPN type triode, which can be distinguished according to these differences.

2. Use the ohm gear of the multimeter to judge

According to the different equivalent circuits, they can be distinguished by the ohm scale of the multimeter. The method is as follows:

Set the multimeter to the appropriate ohm gear (in fact, in the process of measurement, the gear level of the ohm gear should be properly adjusted as required):

(1) Connect the red lead of the ammeter to one pin of the triode, and connect the black lead to the other two pins successively to measure two resistance values.

(2) If these two values are very small (that is, the resistance value is less than a few hundred Ohms), then this triode is a PNP type triode, and the pin that contacts the red probe is its base. b. The further judgment of it is: switch the red and black probes, that is, the black probe contacts the base b. The red probe contacts the other two pins successively, and repeat the measurement. If the measured two resistance values are large, This indicates that this triode is a PNP type triode, and after the red and black pen are switched, the pin that contacts the black pen is its base b, which proves that the original judgment is correct.

(3) Otherwise, repeat step (1) until the two measured resistance values are small or tested more than three times.

(4) If the three pins of the triode are tested with the red pen as the benchmark, but they do not meet the conditions of step (2), then the triode is NPN-type triode, and the further judgment steps are as follows: change the position of the red and black pens, that is, take the black pen as the benchmark, and the red pen is connected to the other two pins respectively. If the two resistance values measured at one time are very small (that is, the resistance value is less than several hundred ohms), it means that the transistor is NPN type transistor, and the pin that contacts the black probe is its base b.