Share knowledge of semiconductor diodes

The core of a semiconductor diode is a PN junction, which is characterized by the characteristics of a PN junction - unidirectional conductivity. The voltammetric characteristic curve is often used to vividly describe the unidirectional conductivity of a diode.

If voltage is the horizontal coordinate and current is the vertical coordinate, the corresponding values of voltage and current are interconnected by smooth curves to form the voltammetric characteristic curve of the diode.

1. Forward characteristics

When a positive voltage is added on both sides of the diode, a positive current is generated. When the positive voltage is small, the positive current is very small (almost zero). This part is called the dead band. The voltage at the corresponding point is called the deadband voltage or threshold voltage (also called the threshold voltage), which is about 0.5V for silicon tubes and 0.1V for germanium tubes.

When the positive voltage exceeds the threshold voltage, the positive current increases sharply and the diode resistance is small and conductive. At this time, the positive on voltage drop amplitude of the silicon tube is about 0.6~0.7V, and the germanium tube is about 0.2~0.3V.

Diode positive guidance on, pay special attention to its forward current can not exceed a higher value, or it will burn the PN junction.

2. Reverse characteristics

When the diode is increased on both sides of the reverse voltage, the diode is equivalent to a particularly large resistance, the reverse current is very small, will not change with the reverse voltage changes. At this point, the current is called reverse saturation current IR.

3. Reverse penetration characteristics

When the diode reverse voltage increases to a certain value, the reverse current increases sharply, known as reverse penetration. The corresponding voltage at this time is called reverse penetration voltage, expressed in UBR.

4. The effect of temperature on the characteristics

Because the core of the diode is a PN junction, its conductivity is related to temperature. When the temperature rises, the positive characteristic curve of the diode shifts to the left and the positive voltage drop decreases; the reverse characteristic curve moves down and the reverse current increases.