How to distinguish between transistor electrodes and diode types, and are there any skills and methods?

How to distinguish between transistor electrodes and diode types, and are there any skills and methods?

   1. Visual inspection

   1. Identification of diod type

   In general, whether the diod type is NPN or PNP should be distinguished from the model number marked on the diode shell. According to the ministerial standard, the second digit (letter) of the transistor type, A and C represent PNP diodes, and B and D represent NPN diodes, for example:

   The 3AX is a PNP type low-frequency low-power diod, and the 3BX is an NPN type low-frequency low-power diode

   3CG is PNP type high-frequency low-power diod, and 3DG is NPN type high-frequency low-power diode

   3AD is a PNP type low-frequency high-power diode, and 3DD is an NPN type low-frequency high-power diode

   3CA is PNP type high-frequency high-power diode, and 3DA is NPN type high-frequency high-power diode

   In addition, there are internationally popular 9011 ~ 9018 series high-frequency and low-power diodes, except for 9012 and 9015 PNP diodes, the rest are NPN diodes.

   2. Identification of diod poles

Commonly used small and medium-power transistors are available in metal round shells and plastic packages (half-cylindrical type), and Figure T305 describes three typical shapes and pole arrangements.

Second, use the multimeter resistance file to distinguish

There are two PN junctions inside the transistor, and the three poles e, b and c can be distinguished by the resistance level of the multimeter. In the case of ambiguous model calling, this method can also be used to determine the diod type.

1. Identification of the base

When identifying the diod pole, the base should be confirmed first. For the NPN diode, use the black watch pen to connect the assumed base, and use the red watch pen to contact the other two poles respectively, if the measured resistance is small, about hundreds of ohms ~ thousands of ohms;

The measured resistance is large, above several hundred thousand ohms, and the black watch pen is connected to the base. PNP diode, the opposite is true, when the two PN junctions are positively deviated during the measurement, the red table pen is connected to the base. Actually, the base of the small power diode is one

Generally arranged in the middle of the three pins, the black and red table pens can be connected to the base respectively by the above method, which can not only determine whether the two PN junctions of the triode are intact (the same as the measurement method of the diode PN junction), but also confirm the diode type.

2. Identification of collector and emitter

After determining the base, assume that one of the remaining pins is the collector c and the other is the emitter e, and pinch the c pole and the b pole respectively with your fingers (i.e., use your fingers instead of the base resistor Rb). At the same time, the multimeter two meter pens are in contact with C and E respectively

If the measuring diod is NPN, then use the black watch pen to contact the c pole, and use the red watch pen to connect the e pole (the PNP diode is opposite), observe the deflection angle of the pointer, and then set another pin to the c pole, repeat the above process, compare the deflection angle of the two measurement pointers, large

indicates that the IC is large, the diod is in an amplified state, and the corresponding assumptions of c and e are extremely correct.