The tube voltage drop after diode forward conduction remains basically unchanged, but the following factors will make the tube voltage drop change slightly:

 

When the temperature rises, the pressure drop of the pipe will decrease slightly; When the temperature decreases, the pipe pressure drop will increase slightly.

 

When the forward current changes greatly, the forward voltage drop will change slightly. That is, when there is a small change in the forward voltage, it will cause a great change in the forward current.

 

The temperature compensation circuit can be designed by using the characteristics that the voltage drop of diode changes slightly with temperature. Without understanding the characteristics of diode when analyzing the temperature compensation circuit, the working principle of the circuit can not be analyzed.