1. The volt-ampere characteristics of the PN junction
2. Capacitance effect of PN junction
The capacitance equivalent to the change in the width of the depletion layer is called the barrier capacitance Cb.
In the diffusion area, the process of accumulation and release of electric charge is the same as the process of charging and discharging of the capacitor, and this capacitance effect becomes the diffusion capacitance Cd.
It is related to the forward current i flowing through the PN junction, the voltage equivalent UT of temperature and the lifetime t of the unbalanced minority carrier. The larger the i, the larger the t, the smaller the UT, the larger the Cd.
The junction capacitance Cj = Cb+Cd, the junction capacitance is usually (1pF-several hundreds of pF), the capacitance of the low frequency signal is large, and the junction capacitance effect is only considered when the signal frequency is high.
That is, in the case of high frequency, the diode can be equivalent to a parallel connection of an ideal diode and a capacitor, and this parallel capacitor will affect the circuit.
3. The volt-ampere characteristics of the diode
The main parameters of the diode
①Maximum rectified current IF Maximum allowable forward average current
②The highest reverse working voltage UR is usually half of the breakdown voltage U (BR)
③Reverse current IR Reverse current when there is no breakdown. The smaller the IR, the better the unidirectional conductivity of the diode, which is very sensitive to temperature.
④The maximum operating frequency fM is the upper limit cut-off frequency of the operation. When it exceeds this value, the diode will not be able to reflect the unidirectional conductivity very well due to the junction capacitance.
4. Zener diode
