Various classifications of crystal diodes 7

11. PIN diode

This is a crystal diode constructed by sandwiching an intrinsic semiconductor (or a semiconductor with low concentration impurities) between the P and N regions. The 'I' in PIN is an English abbreviation for 'intrinsic' meaning. When its operating frequency exceeds 100MHZ. html "target=" -blank "title=" 100MHz ">100MHz, due to the storage effect of minority carriers and the transit time effect in the" intrinsic "layer, the diode loses its rectification function and becomes an impedance element, and its impedance value changes with the bias voltage. In zero bias or DC reverse bias, the impedance of the "intrinsic" region is very high; During DC forward bias, due to carrier injection into the "intrinsic" region, the "intrinsic" region exhibits a low impedance state. Therefore, PIN diodes can be used as variable impedance components. It is often used in high-frequency switches (i.e. microwave switches), phase shifting, modulation, limiting and other circuits.

12. Avalanche diode

It is a transistor that can generate high-frequency oscillation under the action of external 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

It is a crystal diode with 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.