SMD is also called crystal diode, referred to as the diode (diode), in addition, there are early vacuum electron diode; it is a kind of electronic device with unidirectional conduction current. A PN junction two lead terminals in the semiconductor diode, the electronic device according to the direction of applied voltage, the transduction of unidirectional current. Generally speaking, SMD crystal diode p-n junction interface is a p type semiconductor and N type semiconductor formed by sintering. The formation of the space charge layer on both sides of the interface, a built-in field. When the applied voltage is equal to zero, the concentration of p-n nodes on both sides of the difference caused by the carrier diffusion current and induced by the built-in field drift current is equal to the power balance, it is normal under the diode characteristics.
Tube voltage drop SMD: silicon diode (not luminous type) forward voltage drop 0.7V, germanium diode forward voltage drop of 0.3V, light-emitting diode forward voltage drop varies with different colors and different. There are mainly three kinds of color, the pressure drop values are as follows: the pressure drop of red light emitting diode is 2.0--2.2V, the pressure drop yellow light emitting diode is 1.8 2.0V, the pressure drop of the green light emitting diode is 3 3.2V, the rated current of the normal lighting time is about 20mA. Voltage and current is not a linear relationship between the patch diode, so when the patch diode in parallel to meet different resistance is connected.
SMD diode chip diode (English: Diode), electronic components, a device with two electrodes, only allows current from a single direction through. Many use is the application of the function of the rectifier. The varactor diode (Varicap Diode) adjustable capacitor is used as electronic.