The patch diode is a p-n junction interface formed by the sintering of a p-type semiconductor and an n-type semiconductor. When the applied voltage is equal to zero, the diffusion current and the drift current caused by the self-constructed electric field are equal to each other due to the difference in carrier concentration between the two sides of the p-n junction, and this is also the diode characteristic in the normal state. In this article, we mainly describe how to distinguish the positive and negative electrodes of a SMD diode. 

For diode polarity discrimination we mainly complete the following three points:

1. according to the label or shape to determine the polarity

In order to make people better distinguish between the positive and negative diodes, some diodes will mark the surface with positive and negative polarity. Some special diodes can also find positive and negative polarity from the appearance.

2. using an analog multimeter to determine the polarity

For diodes that are not marked with polarity or have no apparent shape, use the ohmic block of the multimeter to determine the polarity. Multimeter to Rx100 or Rx1k block, measuring the resistance between the two pins of the diode, the positive and negative each test once, there will be a resistance of one large and one small, with a small resistance of the subject shall prevail, black table pen for The anode of the diode, the red lead is the cathode of the diode.

3. using a digital multimeter to determine the polarity

Digital multimeter and analog multimeter, there are ohms, but because of the difference between the two measurement principle, digital multimeter ohms can not determine the positive and negative diodes (digital multimeter to measure the positive and negative resistance when the resistance value is displayed infinity symbol "1" ), but the digital multimeter has a diode-specific measurement block that can be used to determine the positive and negative polarity of the SMD diode.

The above method is to distinguish the positive and negative polarities of the patch diodes. The positive and negative diodes of the patch diodes are differentiated. In the circuit, the diodes are connected in a random manner, and if they are light, the diodes cannot work normally, and the diodes are damaged. Therefore, it is particularly important to distinguish the positive and negative electrodes of the SMD diode.