Working principle and category of crystal diodes 5

3. Reverse current

Reverse current refers to the reverse current flowing through a diode at a specified temperature and maximum reverse voltage. The smaller the reverse current, the better the unidirectional conductivity of the tube. It is worth noting that there is a close relationship between reverse current and temperature, with the reverse current doubling for every 10 degrees Celsius increase in temperature. For example, for a 2AP1 germanium diode, if the reverse current is 250uA at 25 o'clock and the temperature rises to 35, the reverse current will increase to 500uA, and so on. At 75 o'clock, its reverse current has reached 8mA, not only losing its unidirectional conductivity, but also causing the tube to overheat and be damaged. For example, the 2CP10 silicon diode has a reverse current of only 5uA at 25 ° C, and when the temperature rises to 75 ° C, the reverse current is only 160uA. Therefore, silicon diodes have better stability than germanium diodes at high temperatures.

Test the quality of the diode

Beginners can use a multimeter to test the performance of diodes in their spare time. Before testing, first turn the conversion switch of the multimeter to the RX1K position in the ohm range (be careful not to use RX1 to avoid excessive current burning out the diode), and then short-circuit the red and black probes to zero the ohm.

1. Positive characteristic test

Connect the black probe (positive terminal inside the meter) of the multimeter to the positive terminal of the diode, and connect the red probe (negative terminal inside the meter) to the negative terminal of the diode. If the pointer does not swing to zero but stops in the middle of the dial, the resistance value at this point is the forward resistance of the diode, and generally the smaller the forward resistance, the better. If the forward resistance is 0, it indicates that the die is short circuited and damaged. If the forward resistance is close to infinity, it indicates that the die is open circuited. Both short-circuit and open circuit pipes cannot be used.