Classification of Crystal Diodes 12

18. Double base diode (single junction transistor) is a three terminal negative resistance device with two bases and one emitter, used in relaxation oscillation circuits and timing voltage readout circuits. It has the advantages of easy frequency adjustment and good temperature stability.

19. Light emitting diodes are made of gallium phosphide and gallium arsenide materials, with small volume and forward driven luminescence. Low working voltage, low working current, uniform light emission, long lifespan, capable of producing red, yellow, and green monochromatic light.

3、 According to their characteristics, point contact diodes are classified into forward and reverse characteristics as follows.

1. Point contact diodes are commonly used in detection and rectification circuits, as the title suggests. They are intermediate products with neither particularly good nor particularly bad forward and reverse characteristics. For example, SD34, SD46, 1N34A, etc. belong to this category.

2. High reverse withstand voltage point contact diodes are products with high maximum peak reverse voltage and maximum DC reverse voltage. Used for detection and rectification of high-voltage circuits. This type of diode generally has poor or average forward characteristics. In point contact germanium diodes, there are SD38, 1N38A, OA81, and so on. This germanium material diode has limited voltage resistance. Higher requirements include silicon alloys and diffusion type.

3. The forward voltage characteristics of high reverse resistance point contact diodes are the same as those of commonly used diodes. Although its reverse withstand voltage is particularly high, its reverse current is small, so its advantage is its high reverse resistance. In circuits with high input resistance and high resistance load resistance, for germanium material high reverse resistance diodes, SD54, 1N54A, etc. belong to this type of diode.

4. A high conductivity point contact diode is the opposite of a high reverse resistance type. Although its reverse characteristic is poor, it makes the forward resistance small enough. For high conductivity point contact diodes, there are SD56, 1N56A, and so on. For high conductivity key type diodes, better characteristics can be obtained. This type of diode has high rectification efficiency when the load resistance is particularly low.