Principles and methods of substitution for rectifier diodes

Rectifying diodes can be replaced with other diodes of the same material and polarity as the original diode, or they can be used in parallel. A PN junction of a transistor can be used instead of a diode. The substitution principles of rectifier diodes mainly include the following points, and substitution should be carried out in accordance with these principles.

The substitute diode must be made of the same material and polarity as the rectifier diode specified in the circuit. This is mainly because the voltage drop of germanium diodes and silicon diodes is different. If they are directly replaced, the circuit will not work properly. The relevant parameter indicators of the substitute diode shall not be lower than those of the original rectifier diode, especially the maximum rectification current and maximum reverse voltage limit parameters, which shall not be lower than those of the original diode, otherwise there is a possibility of burning or breakdown.

Try to use diodes with similar or identical purposes as substitutes. For example, replacing one type of rectifier diode with another type of rectifier diode, replacing the rectifier full bridge with four rectifier diodes, etc.

There are various methods for replacing rectifier diodes, such as parallel connection of two rectifier diodes to increase the operating current. When there are no high current rectifier diodes, two smaller current rectifier diodes can be used in parallel. High power transistor can be used as a substitute for rectifier diode. Directly using a PN junction of a transistor (such as the PN junction between the base and emitter) as a rectifier diode, with the base as the anode and the emitter as the cathode. Even if a PN junction transistor has been burned, it can still be utilized. Connect the base and collector of the transistor together as the positive electrode of the rectifier diode, while keeping the emitter as the negative electrode of the rectifier diode.