The function of diode can describe — with its volt-ampere character—In diode two end add voltage U, measure a voltaic I that has shed diode next, the relation I=f(u) between voltage and electric current is the volt-ampere character curve of diode namely, if pursue,1 is shown.

 

Graph 1: Curve of diode volt-ampere character

 

1, volt-ampere character expression

The volt-ampere character expression of diode can express to be next type:

 

 

Among them ID crosses diode to flow the electric current of two end, UD is diode the pressurization of two end, UT takes 26mv below normal temperature, IS is retrorse and saturated electric current.

 

2, to character

Of volt-ampere character curve right half part is called to character, by the graph 1 visible, should add diode to go up to when voltage is lesser, to electric current small, be equal to almost 0. When diode only two upright voltage exceed some numerical value when Uon, just increasing apparently to electric current. Call Uon dead band voltage. The material of dead band voltage and diode is concerned. The dead band voltage of general silicon detector is 0.5V left and right sides, the dead band voltage of germanium diode is 0.1V left and right sides.

 

After exceeding dead band voltage to voltage, as voltage elevatory, increasing quickly to voltaic general, the relation of electric current and voltage basically is an index curve. By seeing to characteristic curve, the electric current that has shed diode has bigger change, the voltage of two end maintains diode basically however changeless. Through be in similar analysis computation, call this voltage open voltage. The material of open voltage and diode is concerned. The dead band voltage of general silicon detector is 0.7V left and right sides, the dead band voltage of germanium diode is 0.2V left and right sides.

 

3, retrorse character

Of volt-ampere character curve left half part calls retrorse character, by the graph 1 visible, increase retrorse tension when diode, retrorse electric current is very small, and retrorse electric current increases as retrorse voltage no longer, reached saturation namely, this electric current calls retrorse and saturated electric current, express with symbolic IS.

 

If retrorse voltage continues to lift, after should exceeding UBR, retrorse electric current increases quickly, this kind of phenomenon calls puncture, UBR calls retrorse puncture voltage.

 

Puncture hind has one-way conductivity no longer. Ought to point out, produce retrorse puncture not to mean diode to damage. Actually, after retrorse puncture, want to notice to control the numerical value of retrorse electric current only, do not make its too big, can avoid because of overheat burned-out diode. After retrorse voltage drop is small, diode function still may return to normal.

 

4, the influence with characteristic to diode volt-ampere temperature

 

Graph 2: The temperature of diode is characteristic

 

Temperature is elevatory, to character left move, ; room temperature moves below retrorse character around, temperature every are elevatory 1 ℃ ; to pressure fall reduce 2-2.5mV; Near room temperature, temperature every are elevatory 10 ℃ , retrorse electric current increases one times. The temperature character of diode is shown 2 times like the graph.