How to distinguish Schottky diodes from ordinary diodes in terms of appearance

How to distinguish Schottky diodes from ordinary diodes in terms of appearance

Schottky diodes, ordinary diode (including detector diode, rectifier diode, damping diode, switching diode, Flyback diode) is a semiconductor device formed by a PN structure, with unidirectional conductivity. By using a multimeter to detect its forward and reverse resistance values, the electrode of the diode can be identified, and it can also be estimated whether the diode is damaged.

1. Polarity discrimination

Place the multimeter in R&TImes; 100 gears or R&TIMes; 1k gear, connect the two probes to the two electrodes of the diode, measure one result, switch the two probes, and then measure another result. Among the results of the two measurements, one measured a larger resistance value (for reverse resistance) and the other measured a smaller resistance value (for forward resistance). In measurements with low resistance values, the black lead is connected to the positive pole of the diode, while the red lead is connected to the negative pole of the diode.

2. Detection and Evaluation of Single Negative Conductivity Performance

Usually, the forward resistance value of germanium material diodes is around 1k Ω, and the reverse resistance value is around 300. The resistance value of a silicon material diode is about 5 k Ω, and the reverse resistance value is infinity. The smaller the forward resistance, the better, while the larger the reverse resistance, the better. The greater the difference between the forward and reverse resistance values, the better the unidirectional conductivity characteristics of the diode.

If the measured forward and reverse resistance values of the diode are both close to 0 or the resistance value is small, it indicates that the diode has internal breakdown, short circuit, or leakage damage. If the measured forward and reverse resistance values of the diode are both infinite, it indicates that the diode has been opened and damaged.

3. Detection of reverse breakdown voltage

The reverse breakdown voltage (withstand voltage) of the diode can be measured using a transistor DC parameter test table. The method is to set the "NPN/PNP" selection key of the test meter to the NPN state when measuring diodes. Then, connect the positive pole of the tested diode to the "C" socket of the test meter, insert the negative pole into the "e" socket of the test meter, and press the "V (BR)" key. The test meter can indicate the reverse breakdown voltage value of the diode.

A megohmmeter and multimeter can also be used to measure the reverse breakdown voltage of the diode. When measuring, the negative pole of the tested diode is connected to the positive pole of the megohmmeter, and the positive pole of the diode is connected to the negative pole of the megohmmeter. At the same time, a multimeter (placed in a suitable DC voltage range) is used to monitor the voltage at both ends of the diode. If the handle of the megohmmeter is shaken (gradually increasing slowly), and the voltage at both ends of the diode stabilizes without increasing, this voltage value is the reverse breakdown voltage of the Schottky diodes.