Introduction to the characteristics of diodes

Reference

brief introduction

A diode is a device with two electrodes, a PN junction composed of a P-type semiconductor and an N-type semiconductor. Current can only flow in from the anode of the diode and flow out of the cathode. It has a self-built electric field and is generally used in rectifier circuits.

Positive characteristics

In the circuit, the cathode of the diode is connected to the low voltage end, and the anode is connected to the high voltage end. At this time, the diode will be turned on. This state is called forward bias. When the voltage difference between the two ends of the diode is very small, the diode cannot be turned on. Because the current through the diode is very small. Only when the forward voltage of the diode reaches a certain value (the lowest turn-on voltage of silicon diode is 0.6V, the lowest turn-on voltage of germanium diode is 0.2V) will the diode be fully turned on. After turning on, the voltage across the diode remains unchanged (about 0.7V for silicon diodes and about 0.3V for germanium diodes). This situation is called diode forward voltage drop.

Reverse characteristics

In the circuit, when the cathode of the diode is connected to the high voltage end, and the anode is connected to the low voltage end, the diode is in the cut-off state at this time and no current flows. This state is called reverse bias. When the diode is in reverse bias, if there is still a weak current flowing through the diode, this is the leakage state. When the reverse voltage across the ordinary diode reaches a certain value, the reverse current will increase sharply. At this time, the diode will lose its unidirectional conductivity and will be damaged by reverse breakdown.