Semiconductor diode, also known as crystal diode, referred to as diode (diode). The utility model relates to an electronic device capable of conducting current in one direction. There is a PN junction two lead terminals in the semiconductor diode inside the electronic device according to the direction of the applied voltage, with unidirectional current conductivity.
Determine the polarity of the semiconductor diode a, visual method: general circuit in the physical can be seen directly through the eyes of positive and negative poles. The semiconductor diode in the physical in the end if you see the color coded is negative, the other end is positive.
B, with a multimeter (pointer) to judge the polarity of the semiconductor diode: usually choose million ohm file table (R * 100 R * 1K), then use the multimeter two probes are respectively two receiving diode electrode, when the diode conduction resistance of smaller test (generally between tens of ohms to several thousand ohms), then the black pen is connected with the positive electrode of the diode, the red pen is connected with the negative electrode of the diode. When the measured resistance value is very large (usually several hundred to several thousand ohms), then the black pen is connected with the negative electrode of the diode, the red pen is connected with the positive electrode of the diode.
Note: C, testing by digital 000 to measurement of diode with a table, the red pen is connected with the diode cathode, anode black probe connected to the diode, the resistance is positive conducting diode through resistance, and the pointer multimeter probe connected to the opposite method.
Varactor diode is a special diode junction capacitance common diode internal "PN junction" can change with the applied reverse voltage and the change of specially designed according to the principle of. The variode in cordless telephone is mainly used in high frequency modulation circuit of mobile phone or landline, low frequency signal is modulated to the high frequency signal, and send them out. In the working state, the varactor diode modulation voltage is generally applied to the negative electrode, so that the internal capacitance of the varactor diode with the modulation voltage changes.