Classification of Crystal Diodes (2) 5

12. Avalanche diode is a transistor that can generate high-frequency oscillations under the action of an applied voltage. The working principle of generating high-frequency oscillations is Luan's: using avalanche breakdown to inject charge carriers into the crystal. As the charge carriers need a certain amount of time to cross the chip, their current lags behind the voltage, resulting in a delay time. If the transit time is properly controlled, negative resistance effects will occur in the relationship between current and voltage, leading to high-frequency oscillations. It is often applied in oscillation circuits in the microwave field.

13. Tunnel diode is a crystal diode that uses tunneling effect current as the main current component. The base materials are gallium arsenide and germanium. The N-type region of its P-type region is highly doped (i.e. high concentration of impurities). The tunneling current is generated by the quantum mechanical effects of these degenerate semiconductors. The occurrence of tunneling effect requires the following three conditions: ① The Fermi level is located in the conduction band and full band; ② The width of the space charge layer must be very narrow (below 0.01 micrometers); There is a possibility of overlapping holes and electrons in the P-type and N-type regions of degenerate semiconductors at the same energy level. Jiangqi diode is a dual terminal active device. Its main parameters are peak to valley current ratio (IP/PV), where the subscript "P" represents "peak"; And the subscript "V" represents "valley". Jiangqi diodes can be applied in low-noise high-frequency amplifiers and high-frequency oscillators (with operating frequencies up to millimeter wave band), as well as in high-speed switching circuits.

14. A fast turn off (step recovery) diode is also a type of diode with a PN junction. Its structural feature is that it has a steep impurity distribution region at the PN junction boundary, forming a "self electric field". Due to the fact that PN junction conducts with minority carriers under forward bias and has charge storage effect near the PN junction, its reverse current needs to go through a "storage time" before it can reach its minimum value (reverse saturation current value). The "self electric field" of the step recovery diode shortens the storage time, quickly cuts off the reverse current, and generates rich harmonic components. By utilizing these harmonic components, comb like frequency spectrum generation circuits can be designed. Fast turn off (step recovery) diodes are used in pulse and high-order harmonic circuits.