Diode is a PN structure into its main feature is the one-way conductivity, usually expressed in its voltage characteristics.

　　Voltage characteristics diode means current flows through the diode iD relationship with the voltage applied across the diode between vD or curves. Point by point method for measuring or mapping out a transistor Tracer VI curve showing up, saying current characteristic of the diode. Figure 1 is a graphical representation of the diode voltage characteristics, as an example of its properties.

FIG diode voltage characteristics

　　1. Forward Characteristics

　　As can be seen from the figure, when the applied forward voltage is zero, the current is zero; when the forward voltage is small, due to the external electric field is hardly enough to overcome the PN junction within the electric field on the majority carrier diffusion caused by resistance exercise, therefore, the forward current is very small (almost zero), the diode exhibits greater resistance. This curve is called the dead zone. & nbsp;

　When the forward voltage Vth increases to a certain value after the electric field is significantly reduced in the forward current have significantly increased. It is known as the threshold voltage Vth or the valve voltage. Different Vth depending on the material and temperature diode and different, at room temperature, the silicon tube is generally about 0.5V, germanium tube is about 0.1V. In practice, often put forward characteristic relatively straight portion extend in horizontal cross point as the threshold value voltage Vth, as shown in dotted lines and the intersection of the horizontal axis.

　　When a forward voltage is greater than Vth, forward current versus forward voltage is almost linear growth. The forward current increases linearly with the forward voltage corresponding to the forward voltage, called a diode turn-on voltage, represented by VF. Typically, silicon tube turn-on voltage of approximately 0.6 ~ 0.8V, generally taken to be 0.7V; conducting germanium tube voltage of about 0.1 ~ 0.3V generally taken to be 0.2V.

　　2. Reverse Characteristics

　　When the reverse voltage is applied across the diode, PN junction internal electric field to further enhance the diffusion more difficult. Only the minority carriers drift motion in the reverse voltage is applied to the formation of a weak reverse current IR. Reverse current is very small, and within a certain range increases with almost no reverse voltage is increased. But the reverse current is a function of temperature will vary with changes in temperature. At room temperature, low power silicon tube reverse current in nA magnitude, germanium tube reverse current at & mu; A magnitude.

　　3. Reverse breakdown characteristics

　　When the reverse voltage is increased to a certain value VBR, reverse current surge, a phenomenon known as breakdown diodes, the voltage value at this time is called the breakdown voltage VBR, VBR depending diodes may be, generally at ordinary diode tens of volts and silicon germanium tube tube relatively high. & nbsp;

　Breakdown characteristic feature is that although the reverse current surge, but the terminal voltage of the diode has changed little, this feature has become the basis for the production of the zener diode.

4. Effect of temperature on the diode voltage characteristics of

　　Diodes are temperature sensitive device, temperature changes its volt-ampere characteristics of mainly as follows: As the temperature increases, the forward curve to the left, that is the forward voltage drop decreases; reverse characteristic curve downward that the reverse current increases. Usually near room temperature is increased by 1 ℃, its forward voltage drop is reduced 2 ~ 2.5mV; temperature is increased by 10 ℃, the reverse current increases about 1 times.

　In summary, the voltage characteristic diode has the following characteristics:

　① diode has a way conductivity;

　② diode voltage characteristic nonlinear;

　③ diode voltage characteristics and temperature.