What is a smd led diode

27 Feb 2020

A smd led diode is a device with two electrodes in an electronic component that allows current to flow in only one direction. Many uses are made by its rectifying function. Varicap Diode is used as an electronic adjustable capacitor. The directivity of the current of most diodes is usually called "Rectifying" function. Therefore, the diode can be thought of as an electronic version of a check valve.

The early vacuum electronic diode was an electronic device capable of conducting current unidirectionally. There is a PN junction and two lead terminals inside the semiconductor diode. This electronic device has unidirectional current conductivity according to the direction of the applied voltage.

Generally speaking, a crystal diode is a p-n junction interface formed by sintering a p-type semiconductor and an n-type semiconductor. Space charge layers are formed on both sides of the interface to form a self-built electric field. When the applied voltage is equal to zero, the diffusion current caused by the difference in carrier concentration on both sides of the p-n junction is equal to the drift current caused by the self-built electric field, and it is in the state of electrical equilibrium, which is also a normal diode characteristic.

Characteristic
Positiveness. When a forward voltage is applied, at the beginning of the forward characteristic, the forward voltage is small enough to overcome the blocking effect of the electric field in the PN junction, and the forward current is almost zero. This forward voltage that cannot turn on the diode is called the dead-band voltage. When the forward voltage is greater than the dead-band voltage, the electric field in the PN junction is overcome, the diode conducts forward, and the current rises rapidly with increasing voltage.

In the current range of normal use, the terminal voltage of the diode remains almost unchanged when it is turned on. This voltage is called the forward voltage of the diode. When the forward voltage across the diode exceeds a certain value, the internal electric field is quickly weakened, the characteristic current rapidly increases, and the diode conducts forward. This value is called the threshold voltage or threshold voltage. The silicon tube is about 0.5V and the germanium tube is about 0.1V.

Reverse. When the applied reverse voltage does not exceed a certain range, the current through the smd led diode is a reverse current formed by the minority carrier drift motion. Because the reverse current is small, the diode is in the off state.

Electric breakdown
When the applied reverse voltage exceeds a certain value, the reverse current will suddenly increase. This phenomenon is called electrical breakdown. The threshold voltage that causes electrical breakdown is called the diode reverse breakdown voltage. The diode loses unidirectional conductivity during electrical breakdown. When using it, avoid excessive reverse voltage applied by the diode.

A diode is a two-terminal device with unidirectional conductivity. It is divided into an electronic diode and a crystal diode. Because of the heat loss of the filament, the electronic diode has a lower efficiency than the crystal diode, so it is rarely seen now. It is more common and commonly used. It is a crystal diode.

The unidirectional conductivity of diodes, semiconductor diodes are used in almost all electronic circuits, plays an important role in many circuits, is one of the earlier semiconductor devices.

Diode tube voltage drop: The forward voltage drop of a silicon diode is 0.7V, the forward voltage drop of a germanium tube is 0.3V, and the forward voltage drop of a light-emitting diode will vary with different light-emitting colors. There are three main colors, and the specific voltage drop reference values ​​are as follows: the voltage drop of the red LED is 2.0-2.2V, the voltage drop of the yellow LED is 1.8-2.0V, and the voltage drop of the green LED is 3.0-3.2V, which is normal. The rated current during light emission is about 20mA.

The voltage and current of the diodes are not linear, so when different diodes are connected in parallel, an appropriate resistance should be connected.

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