Basic Knowledge Points of Diodes

Anita Chan Anita Chan 05 January
Basic Knowledge Points of Diodes



In the family of electronic components, There is a particular kind that allows the flow of current in one direction. It's a two-electrode device known as a diode.


The Early Diode


The first diodes to be discovered include the Cat's Whisker Crystals along with Thermionic Valves. It is based on the heating of electrons from the cathode to the anode in order to achieve conduction.

If the negative and positive poles connected to the power source are in reverse the power supply is unable to conduct electricity. Diodes of the past could conduct current in only one direction. The first electronic diodes faced issues including their dimensions, preheating, high power consumption, and brittleness that led to the creation of crystal diodes.


 Basic Knowledge Points of Diodes

Crystal Diode


Crystal diodes can also be referred to as semiconductor diodes. There's a PN junction as well as two terminals within this semiconductor diode. It is distinguished in the conductivity of the unidirectional current. Diodes used in everyday life typically make use of semiconductor materials.


Crystal Diode Structure


In relation to the structure of crystal diodes, we need to first comprehend the three main concepts in the context of PN junction.


In the event that the P-type semiconductor, as well as the N-type semiconductor, come into contact, a distinct interface of PN junction is created as well as space charge layers form across both the sides, creating an electric field self-built. Diodes that conduct in a unidirectional manner are created through the use of PN junction as their primary structure, then adding pins or leads.


Basic Knowledge Points of Diodes


Crystal Diode Classification


Crystal diodes are classified in accordance with different materials as well as different PN junctions.


1. Point Contact Diode


When we press the metal pin onto a single wafer made of germanium or silicon and a point-contact diode will be created by the current method.

The electrostatic capacitance at the PN junction in the diode that is point-contact is very small. Thus, high-frequency circuits can be used as point contact diodes. Because of their simple design, their price is reasonable. For general applications like detection of rectification, modulation mixing, and the limitation of signals with small amounts It is a device with a larger application. As compared to the type of junction on the surface it has a disadvantage. The main reason for this diode with a point contact is that its forward and reverse characteristics are both weak. This means it can't be employed in high-current and rectifying.




2. Surface Contact Diode


The diode with a surface contact has an extensive "PN junction" area, which permits massive currents (several amperes up to tens of amps) to flow through, and is typically used in the "rectifier" circuit that converts the alternating current into direct current. Surface contact crystal diodes are commonly employed in high-current switches.



3. Planar Diode


The planar diode is a special silicon diode. It is named for the way in which the semiconductor's surface is flat.

On the single silicon wafer (mainly single silicon of the N-type) P-type impurities get dispersed and the shielding function from the film that covers the wafer's surface is employed. The PN bonding surface is covered with an oxide film that has excellent stability and longevity. It is not just able to carry higher currents, but also provides robust and stable performance. It is therefore ideal for pulse, switching, and high-frequency circuits.




For more relevant information about diodes here!


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