Distinguishing the quality of crystal diodes 1

To determine the quality of a diode, the following methods can be used:

1. Use a multimeter R * 100 or R * 1K to measure the forward and reverse resistance of the diode, as shown in Figure 7. The forward resistance of a 2AP diode with germanium point contact is around 1K, as shown in Figure 7a, and the reverse resistance should be above 100K, as shown in Figure 7b; the forward resistance of a 2CP diode with silicon surface contact is around 5K, and the reverse resistance should be above 1000K. In short, the smaller the forward resistance, the better, and the larger the reverse resistance, the better. But if the forward resistance is too large or the reverse resistance is too small, it indicates that the detection and rectification efficiency of the diode is not high. As shown in Figure 8, if the forward resistance is infinite (the pointer does not move), it indicates an internal circuit break in the diode; If the reverse resistance is close to zero, it indicates that the diode has broken down. Internal disconnected or broken down diodes cannot be used.

Figure 8

If there is no multimeter, the battery, speaker (or headphones), and the tested diode can also be connected in series. When the negative terminal of the diode is connected to the positive terminal of the battery, and the positive terminal is connected in series with a horn and then connected to the negative terminal of the battery (reverse connection), intermittently connected, if the horn makes a loud "clucking" sound, it indicates that the diode has been triggered (as shown in Figure 9a); On the other hand, if the diode is continuously connected in the forward direction (as shown in Figure 9b), and there is no sound from the horn, it indicates that there is an internal circuit break in the diode.

Summary: Semiconductors are substances with special properties. They are not completely conductive like conductors, nor are they non-conductive like insulators. They are in between the two, so they are called semiconductors. The two most important elements in semiconductors are silicon (pronounced "gui") and germanium (pronounced "zhe"). We often hear about Silicon Valley in the United States because there were many semiconductor manufacturers there at the beginning.diode