A diode is an electronic device made of semiconductor materials (silicon, selenium, germanium, etc.). It has unidirectional conductivity, that is, the diode is turned on when a forward voltage is applied to the anode and cathode of the diode. When reverse voltage is applied to the anode and cathode, the diode is turned off. Therefore, the on and off of the diode is equivalent to the on and off of the switch.
Diode is one of the earliest semiconductor devices, and its application is very extensive. Especially in various electronic circuits, using diodes and resistors, capacitors, inductors and other components to make reasonable connections to form circuits with different functions can achieve rectification of AC power, detection of modulated signals, limiting and clamping, and power supply Various functions such as voltage stabilization.
Point contact diode Point contact diodes have a small PN junction contact area and cannot pass large forward currents and withstand high reverse voltages. However, its high-frequency performance is good and it is suitable for use in high-frequency detection circuits and switching circuits.
Surface contact diode The surface-contact diode has a large PN junction contact area, can pass a large current, and can withstand a high reverse voltage, which is suitable for use in rectifier circuits.
Planar diode The planar diode has a small PN junction area when used as a switching tube in a pulsed digital circuit, and a larger PN junction area when used for high-power rectification.
Zener Zener tube is a special surface contact type semiconductor silicon diode, which has the function of stabilizing voltage. The main difference between a zener tube and an ordinary diode is that the zener tube works in the reverse breakdown state of the PN junction. By restricting the magnitude of the reverse current during the manufacturing process and during use, it can be ensured that the voltage regulator tube will not be damaged by overheating in the reverse breakdown state. The zener diode is different from ordinary diodes. Its reverse breakdown is reversible. As long as it does not exceed the allowable value of the zener current, the PN junction will not be overheated and damaged. The original performance, so the voltage regulator has good repeated breakdown characteristics.
Photodiode Photodiodes are also called photodiodes. It has a glass window on its case for easy access to light. Its characteristic is that when light is irradiated to its PN junction, free electrons and holes can be generated in pairs, so that the concentration of minority carriers in the semiconductor is increased. The current increases. Therefore, its reverse current increases linearly with increasing light intensity. When there is no light, the volt-ampere characteristics of photodiodes are the same as ordinary diodes. Photodiode as a light control element can be used in various object detection, photoelectric control, automatic alarm and so on. When made into a large-area photodiode, it can be regarded as a source of energy and called a photovoltaic cell. At this time, it does not need an external power supply, and can directly convert light energy into electricity.
led A light emitting diode is a semiconductor solid-state display device that directly converts electrical energy into light energy, referred to as LED. Similar to ordinary diodes, light emitting diodes are also made of a PN structure. The PN junction of the light emitting diode is packaged in a transparent plastic case, and the shapes are square, rectangular, and circular. Light-emitting diodes have low driving voltage and small working current, and have strong resistance to vibration and shock, small size, high reliability, low power consumption and long life. They are widely used in signal indicating circuits. In the digital tube commonly used in electronic technology, the principle of light-emitting diodes is opposite to that of photodiodes. When a light-emitting diode is forward-biased through a current, it emits light. This is due to the energy released when the electron and hole are directly recombined. Its spectral range is relatively narrow, and its wavelength is determined by the basic materials used.
Semiconductor diodes are used in almost all electronic circuits. The use of semiconductor diodes in the circuit can protect the circuit and extend the life of the circuit. The development of semiconductor diodes has made integrated circuits more optimized and has played an active role in various fields. Diodes play many roles in integrated circuits and maintain their normal operation.
Light-emitting diodes are widely used in the indicators of various electronic products, light sources for optical fiber communications, indicators of various instruments, and lighting. Many characteristics of light-emitting diodes are unmatched by ordinary light-emitting devices. The main characteristics are: safety, high efficiency, environmental protection, long life, fast response, small size, and solid structure. Therefore, the light emitting diode is a light source that meets the requirements of green lighting.