Diodes face contact surface area contact or said PN junction diode is made of an alloy method or diffusion method, since such a large area of ??the PN junction diode, 1N47 series diode, can withstand high current, but electrode capacitance also large. Such devices are suitable for rectification, but not for high-frequency circuits. Key type key type diode is molten gold or silver threads on a single chip or silicon germanium formed. Its characteristics between point-contact diodes and diode alloys. Compared with point-contact, although key PN junction diode capacity slightly increased, but the positive feature is particularly good. More for switching, 1N52 series diode, sometimes applied to detection and power rectifier (less than 50mA). In the key-type diodes, welding diodes sometimes called gold gold key type, welding silver diode is sometimes called silver key type. Measuring positive and negative resistance with a multimeter R × 1k or R × 10k file, measuring diac positive and negative resistance. Normally its positive and negative resistance should be infinity. If the measured positive and negative resistance values ??are very small or 0, it shows that the diode breakdown. Measuring voltage measuring diac turn turning voltage There are three ways. The first method is: the positive megger (E) and negative (L), respectively, then the diac both ends, with a Megger provides a breakdown voltage while measuring the voltage value of the DC voltage profile with a multimeter, diodes, DIAC will then measured once the poles reversed. Compare the bias voltage value of the two measurements (usually 3 ~ 6V). This deviation is smaller, the better the performance of the diode. The second method is: first with a multimeter measure the mains voltage U, and the measured way trigger diode string into the multimeter's AC voltage measuring circuit, the access mains voltage, read voltage value U1, then the diac and read voltage values ??U2 poles reversed after connection. If the voltage value U1 and U2 are the same, but with different voltage values ??U, LL34 series diode, it shows that the bidirectional trigger diode conduction properties with good symmetry. If U1 and U2 voltage value difference is large, it indicates that the bidirectional trigger diode continuity asymmetry. If U1, U2 voltage values ??are with the mains U are the same, it indicates that the DIAC internally short-circuit damage. If U1, U2 voltage values ??are 0V, the description of the diac internal open damaged. The third method is: 0 ~ 50V continuously adjustable DC power supply, the power of positive series with a 20kΩ resistor after the end of the two-way trigger diode phase, the negative power supply series multimeter current file (which is set at 1mA file) after the two-way trigger the other end of the diode phase. Gradually increase the power supply voltage, a more obvious when the ammeter pointer swing (tens of microamps or more), then this has been a two-way trigger diode turns on, then the power supply voltage that is the breakover voltage of the diac. Figure 4-73 is a bidirectional detection voltage diode turn trigger. Reverse diode characteristics of the applied reverse voltage does not exceed a certain range, current through the diode is a minority carrier drift motion of the reverse current form. Since the reverse current is small, the diode is in the off state. The reverse current is also called the reverse saturation current or leakage current, diode reverse saturation current greatly affected by temperature. Generally silicone tube reverse current is much smaller than the germanium tube, reverse saturation current at low power silicon tube nA magnitude, low-power germanium tube μA magnitude. When the temperature rises, heating the semiconductor excitation, a small number of the number of carriers increases, the reverse saturation current increases. Glass diodes _ gold credit (certified) _ diode provided by Qingdao integrity Technology Co., Ltd. Qingdao integrity Technology Co., Ltd. (www.qdjcx.com) is in Qingdao, Shandong diode leaders, over the years, the company is implementing the scientific management, innovation and development, the principle of honesty and trustworthiness, and satisfy customer needs. Ethical Leadership in gold with the staff warmly welcome all inquiries negotiations to create a better future gold credit.