The forward characteristic is the relationship between the voltage and current when the diode is forward biased. When the forward voltage applied to the two ends of the diode is small, the external electric field generated by the forward voltage is not enough to cause the multiton to form a diffusion movement. At this time, the diode has not actually turned on well. It is usually called the "dead zone", and the diode is equivalent. For a very large resistance, the forward current is very small.
When the forward voltage exceeds a certain value, the internal electric field is greatly weakened, and the multipliers form a diffusion movement under the action of the external electric field. At this time, the forward current increases rapidly with the increase of the forward voltage, and the diode is turned on. This voltage is called the threshold voltage (also called the threshold voltage) and is represented by Vth. At room temperature, the Vth of the silicon tube is about 0.5V, and the Vth of the germanium tube is about 0.1V.
Once the diode is turned on, with the slight increase in the forward voltage, the forward current will increase greatly. At this time, the resistance of the diode is very small, and it can be considered that the diode has a constant voltage characteristic. The forward voltage drop of the diode silicon tube is about 0.6~0.8V (usually 0.7V), and the germanium tube is about 0.2~0.3V (usually 0.2V).
