What is the role and working principle of a diode, what is the role and working principle of a diode

There are many types of diodes, such as TVS transient suppression diodes, ESD electrostatic protection diodes, Schottky diodes, rectifier diodes, voltage regulator diodes, fast recovery diodes, switching diodes, etc., different types of diodes, their working principles and functions are different, the role of the voltage regulator diode is voltage stabilization, the role of the rectifier diode is rectification, the TVS diode is anti-surge overvoltage protection, and the ESD diode is to play the role of electrostatic protection.

Bidirectional TVS diode.

Transient Suppression TVS Diodes.

TVS diodes.

As follows:

Diode. The main principle is to use the PN junction.

The one-way conductivity of the P-n junction is added to the lead and package to become a diode. A crystal diode is a semiconductor made of p-type.

The p-n junction formed with n-type semiconductors forms a space charge layer on both sides of its interface, and a self-built electric field is built. In the absence of an applied voltage, the diffusion current caused by the difference in carrier concentration on both sides of the PN junction and the drift current caused by the self-generated electric field are equal.

When there is a forward voltage bias in the external area, the mutual suppression effect of the external electric field and the self-built Dongchun shirt electric field increases the diffusion current of the carriers and causes the forward current. When there is a reverse voltage bias in the outside world, the external electric field and the self-built electric field are further strengthened to form a reverse saturation current that is independent of the reverse bias voltage value within a certain reverse voltage range.

Main classifications:

Point-contact diodes.

The contact area of the PN junction of the point contact diode is small, and it cannot pass the large forward current and withstand the high reverse voltage, but it has good high-frequency performance and is suitable for use in high-frequency detection circuits and switching circuits.

Face contact diodes.

The PN junction contact area of the surface contact diode is large, and it can withstand a high reverse voltage through a large current in the nanocavity, so it is suitable for rectifier circuits.

. Planar diodes.

Planar diodes are used as switches in pulsed digital circuits with a small pn junction area, and large when used for high-power rectification.

The working principle of the diode: the crystal diode is a p-n junction formed by a p-type semiconductor and an n-type semiconductor, which forms a space charge layer on both sides of the interface of its cavity and failure, and has a self-built electric field.

In the absence of an applied voltage, the diffusion current caused by the difference in carrier concentration on both sides of the PN junction and the drift current caused by the self-generated electric field are equal. When there is a forward voltage bias in the external area, the mutual suppression effect of the external electric field and the self-built electric field increases the diffusion current of the carriers and causes the forward current.

When there is a reverse voltage bias in the outside world, the external electric field and the self-built electric field are further strengthened to form a reverse saturation current i0 that is independent of the reverse bias voltage value within a certain reverse voltage range.

The most important characteristic of diodes is their unidirectional conductivity. In a circuit, current can only flow in from the positive pole of the diode and out from the negative pole. In electronic circuits, the positive pole of the diode is connected to the high potential end, and the negative pole is connected to the low potential end, and the diode will be turned on, which is called forward bias.

In electronic circuits, the positive pole of the diode is connected to the low potential end, and the negative terminal is connected to the high potential end, at this time there is almost no current flowing through the diode, and the diode is in a cut-off state at this time, this connection method is called reverse bias.

The main parameters of the diode

1. Rated forward working current: refers to the maximum forward current value allowed to pass through the diode when it works continuously for a long time. When the current passes through the tube, the die heats up, and when the temperature exceeds the allowable limit (about 140 for silicon tubes and about 90 for germanium tubes), the die will overheat and be damaged.

Therefore, the diode should not exceed the rated forward dry section working current value of the diode.

2. Maximum reverse working voltage: When the reverse voltage added to both ends of the diode reaches a certain value, the tube will break down and lose the unidirectional conductivity. In order to ensure safe use, the maximum reverse operating voltage value is specified.

For example, the reverse withstand voltage of the IN4001 diode is 50V, and the reverse withstand voltage of the In4007 is 1000V.

3. Reverse current: refers to the reverse current of the diode flowing through the diode under the action of the specified temperature and the maximum reverse voltage. The smaller the reverse current, the better the unidirectional conductivity of the tube.