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Introduction of diode working principle
Apr 11, 2018

1. Positive characteristics

In the electronic circuit, the positive pole of the diode is connected to the high potential end, and the negative terminal is connected to the low potential end, and the diode will lead to it. This connection mode is called forward bias. It must be noted that, when the forward voltage applied to both ends of the diode is very small, the diode still fails to guide and the forward current through the diode is very weak. Only when the forward voltage reaches a certain value (which is called the "threshold voltage", the germanium tube is about 0.2V, and the silicon tube is about 0.6V), the diode can be directly connected. The voltage at both ends of the diode is basically unchanged (the germanium tube is about 0.3v and the silicon tube is about 0.7v), which is called the "positive pressure drop" of the diode.

2. Reverse characteristics

In electronic circuit, diode on the low voltage side of the anode, cathode in the high voltage side, now almost no current flows through the diode, the diode is by the state, the connection way, known as reverse biased. When the diode is in the reverse bias, there will still be a faint reverse current flowing through the diode, known as the leakage current. When the reverse voltage on both ends of the diode increases to a certain value, the reverse current will increase sharply, and the diode will lose the single directional conduction characteristic, which is called the breakdown of the diode.

The main parameters of a diode.

Used to indicate the performance of the diode and the applicable range of technical indicators, known as diode parameters. Different types of diodes have different characteristic parameters. For beginners, the following main parameters must be understood:

1. Rated forward working current.

Is the maximum forward current that is allowed to pass through a diode in a long - term continuous work. As the current passes through the tube, the tube core heats up, the temperature rises, and the temperature exceeds the allowable limit (the silicon tube is about 140, and the germanium tube is about 90), which can cause the tube core to overheat and damage. Therefore, the diode should not exceed the rated positive working current value of the diode. For example, the nominal positive working current of the commonly used in4001-4007 germanium diodes is 1A.

2. Maximum reverse working voltage.

When the reverse voltage at both ends of the diode is high to a certain value, the tube will be punctured and the unidirectional conductivity will be lost. In order to ensure the safety, the maximum reverse working voltage value is specified. For example, the reverse pressure of IN4001 diode is 50V and the reverse pressure of IN4007 is 1000V.

3. Reverse current

The reverse current is the reverse current of the diode through the diode at the specified temperature and the maximum reverse voltage. The smaller the reverse current, the better the electrical performance of the single-side guide. It is worth noting that the reverse current is closely related to the temperature, and the reverse current is doubled by about 10. Type 2 ap1 germanium diodes, for example, when 25 if reverse current of 250 ua, temperature rises to 35, reverse current will rise to 500 ua, and so on, in 75, when its 8 ma, reverse current has reached not only lost the single direction of electrical conductivity, still can make the pipe overheating and damage. For example, 2CP10 silicon diode, at 25, the reverse current is only 5uA, and when the temperature rises to 75, the reverse current is only 160uA. Therefore, silicon diode has better stability than germanium diode in high temperature.


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