Diode is one of the most commonly used electronic components, its biggest feature is single guide electricity, is the current can only from one direction through the diode, the diode rectifier circuit, detection circuit, voltage regulator circuit, modulation circuit, are mainly composed of diode to, its principle is very simple, it is the creation of the diodes and other components, is we are now in the rich and colorful electronic information the birth of the world, since the role of the diode is so big so we should how to detect the components, actually very simple just with a multimeter to reverse resistance if small resistance measurement to clarify the diode is bad,
This explains that the diode is good.
We should firmly control the working principle and the basic circuit of such a fundamental component, so as to lay a good foundation for the future study of electronic technology.
A diode consists of a core, a shell and two electrodes.
The tube core is a PN junction. A lead wire is drawn at each end of the PN junction, and plastic, glass or metal materials are used as the packaging shell to form the crystal diode, as shown in the figure below.
The electrode extracted from the P region is called the positive electrode or anode, and the electrode extracted from the N region is called the negative electrode or cathode.
The volt-ampere characteristics of the diode the center of a semiconductor diode is a PN junction, and its characteristics are the characteristics of the PN junction - single conductivity.
The volt-ampere characteristic curve is often used to visualize the single - circuit conductivity of diodes.
If the voltage and current are taken as the abscissa and the ordinate, the corresponding values of voltage and current are connected with smooth curves by drawing method, the volt-ampere characteristic curve of diode is formed, as shown in the figure below (the dotted line is the volt-ampere characteristic of germanium tube, and the solid line is the volt-ampere characteristic of silicon tube).
The volt-ampere characteristic curve of diode is illustrated below:
1. Positive characteristics
On both ends of the diode and the forward voltage, forward current, when the forward voltage is small, little forward current (almost zero), A local called dead zone, the corresponding A) and (A '), called dead zone voltage or voltage threshold voltage (also called A threshold voltage), silicon tube is about 0.5 V, germanium tube is about 0.1 V, as shown in figure of OA (OA) 'section.
When the forward voltage exceeds the threshold voltage, the forward current will increase sharply and the diode will be in the on state with little resistance.
At this time, the positive pressure drop of silicon tube and germanium tube is about 0.6-0.7v and 0.2-0.3v respectively, as shown in section AB (A 'B').
When the diode is on, pay special attention to its positive current cannot exceed the maximum value, otherwise it will burn the PN junction.
2. Reverse characteristics
When the reverse voltage is applied to both ends of the diode, the diode is equivalent to a very large resistance in a wide range of the beginning, and the reverse current is very small and does not change with the reverse voltage.
The current at this time is called the reverse saturation current IR, as shown in the OC (OC ') section of the figure.
3. Reverse breakdown characteristics
When the reverse voltage of diode is added to a certain value, the reverse current increases sharply. This phenomenon is called reverse breakdown.
At this time, the corresponding voltage is called reverse breakdown voltage, which is represented by UBR, as shown in the CD (C 'D') segment in figure 1.11.
4. Influence of temperature on properties
As the center of the diode is a PN junction, its conductivity is related to the temperature. When the temperature rises, the positive characteristic curve of the diode moves to the left, and the positive pressure drop decreases.
When the reverse characteristic curve moves down, the reverse current increases.
Diode classification
Classification by semiconductor data
Diodes can be divided into germanium {Ge} diode, silicon {Si} diode, gallium arsenide {GaAs} diode, gallium phosphate {GaP} diode, etc.
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Two, according to packaging classification
The diode can be divided into plastic diode, glass diode, metal diode, chip diode, no lead cylindrical diode.