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The longer of the two leads of the LED is the positive pole and should be connected to the positive pole of the power supply. Some of the LEDs have the same length of the two leads, but the tube has a raised small tongue, and the lead near the small tongue is the positive. Compared with small incandescent bulbs and xenon lamps, LEDs are characterized by low operating voltage (some only a few volts); low operating current (some can only be illuminated at a few milliamps). Impact and shock resistance Good, high reliability, long life; the intensity of the light can be easily modulated by the intensity of the current passing through the modulation. Due to these characteristics, patch diodes are used as light sources in some optoelectronic control devices and as signal displays in many electronic devices. The tube is made into strips, and 7 strip-shaped LED tubes are used to form a 7-segment semiconductor digital tube, and each digital tube can display 0 to 9 ten words.
The core of the chip diode is a wafer composed of a P-type semiconductor and an N-type semiconductor. There is a transition layer between the P-type semiconductor and the N-type semiconductor, which is called a PN junction. In some PN junctions of semiconductor materials, the injected minority carriers recombine with the majority carriers to release excess energy in the form of light, thereby directly converting electrical energy into light energy. The PN junction is added with a reverse voltage, and minority carriers are difficult to inject, so they do not emit light. Such a diode fabricated by the principle of injection electroluminescence is called a light-emitting diode, and is generally called an LED. When it is in the forward working state (ie, the forward voltage is applied to both ends), when the current flows from the anode of the LED to the cathode, the semiconductor crystal emits light of different colors from ultraviolet to infrared, and the intensity of the light is related to the current.