There are many types of crystal diodes. According to the semiconductor materials used to make ADC08B200CIVS, it can be divided into germanium diodes and silicon diodes. According to its different uses, it can be divided into detection diodes, rectifier diodes, voltage regulator diodes, switch two-board tubes, light-emitting diodes, etc. According to the die structure, it can be divided into point contact diodes, surface contact diodes and planar diodes.
Point-contact diodes use a very thin metal wire to press on the surface of a clean semiconductor wafer, and pulse current is applied to make one end of the contact wire and the wafer firmly sintered together to form a "PN junction". Since the point contact diode is a point contact, only a small current (not more than tens of mA) is allowed to pass, and it cannot withstand higher voltages and pass larger currents, so it is only suitable for small current rectification. But because of the small contact point, the PN junction capacitance is also small and the operating frequency is high, so it is suitable for high-frequency circuits. Point contact diodes are usually used for detection, small current rectification or high frequency switching circuits.
The surface contact diode has a large "PN junction" area, and its working current and can withstand power are large, allowing large currents (several A to tens of A) to pass, and its reverse breakdown voltage is also high . However, due to the large PN junction capacitance, the applicable frequency is low, and it is not suitable for application in high-frequency circuits. Surface contact diodes are usually used in circuits such as rectification, voltage stabilization, and low-frequency switching. For example, 1N4001 to 1N4007 are commonly used rectifier diodes.
The planar diode is a special silicon diode, which can not only pass larger currents, but also has stable and reliable performance. It is mostly used in switching circuits, pulse circuits and high-frequency circuits.
The role of crystal diodes
Types and functions of crystal diodes: We connect the crystal diode to the switch position in the circuit of Figure 3-1 (as shown on the left). The light bulb glows, indicating that the diode is turned on at this time, and the resistance of the diode (called forward resistance) is very small. If the two poles of the diode are reversed (as shown in the picture on the right), the light bulb will not light up at this time. At this time, the resistance of the diode (called the reverse resistance) is very large, and there is almost no current in the circuit. This phenomenon shows that the diode has the characteristics of unidirectional conduction. Using this characteristic of diodes, diodes can be used for detection and rectification.