How to judge the performance of a patch transistor

Multimeter Rx10K block, measure the penetration current of patch transistor, For FNPN type: connect the black test lead to the collector C and the red test lead to the emitter E. Looking at the pointer change, then we can trigger the following mark:

1. The resistance is very small, indicating that the penetration current is large

,

It is close to breakdown and poor stability.

2. The resistance value is zero, indicating that the tube has broken down.

3. The resistance is infinite, indicating that the internal pipe is open.

4. The resistance value constant or resistance value gradually decreases, indicating that the tube is noisy and unstable

It should not be adopted.

For PNP type SMD transistor: connect the red test lead to the collector C and the black test lead to the emitter E

. Observing the pointers, the following

Summary:

1. The resistance is very small, indicating that the penetration current is large

, Already close to breakdown, poor stability.

2. The resistance value is zero, indicating that the tube has broken down.

3. The resistance is infinite, indicating the inside of the tube

Open circuit.

4. The resistance value constant or resistance value gradually decreases, indicating that the tube is noisy and unstable

It should not be adopted.

Note: During the test, the soldering iron can be placed close to the test patch transistor,

Heating, observe the change of the multimeter pointer to determine the current change, if the resistance value after heating

It is significantly lower than before heating, indicating that the thermal stability of the patch transistor is poor.