The basic principle is to use the formed Schottky barrier on the contact surface between metal (such as lead) and semiconductor (N-type silicon wafer) to block reverse voltage.
Most diodes can be used as limiters. There are also specialized limiting diodes such as protective instruments and high-frequency Zener diodes.
The low-power diode used for automatic frequency control (AFC) and tuning is called a varactor diode.
This is a crystal diode constructed by sandwiching an intrinsic semiconductor (or a semiconductor with low concentration impurities) between the P and N regions.
It is also a diode with a PN junction. Its structural feature is that it has a steep impurity distribution region at the PN junction boundary,
TVP tube provides fast overvoltage protection for circuits
