What is a switching diode and how it works

Switching diode is a kind of semiconductor diode, which is specially designed and manufactured for "on" and "off" in the circuit. The time required for it to change from turn-on to cut-off or from cut-off to turn-on is shorter than that of ordinary diodes. The time from the cutoff (high resistance state) to the turn-on (low resistance state) of the switching diode is called the turn-on time; the time from the turn-on to the cut-off time is called the reverse recovery time; the sum of the two times is called the switching time. Generally, the reverse recovery time is greater than the turn-on time, so only the reverse recovery time is given on the use parameters of the switching diode.
When the semiconductor diode is turned on, it is equivalent to the switch closed (the circuit is turned on), and the cut-off time is equivalent to the switch (the circuit is cut off), so the diode can be used as a switch, and the commonly used model is 1N4148. Because the semiconductor diode has the characteristic of unidirectional conduction, the PN junction turns on under the positive bias voltage, the resistance in the on state is very small, about tens to hundreds of ohms; in the reverse bias voltage, it is in the cut-off state, its resistance is very large, generally silicon diodes are more than 10 ohms, germanium diodees also have tens of thousands of ohms to hundreds of kiloohms. Making use of this characteristic, the diode will play the role of controlling the current on or off in the circuit and become an ideal electronic switch.
Under the condition of high frequency, the barrier capacitance of the diode shows a very low impedance and is in parallel with the diode. When the capacitance of the barrier capacitor reaches a certain degree, it will seriously affect the switching performance of the diode. Under extreme conditions, the diode will be short-circuited, and the high-frequency current will no longer pass through the diode, but directly bypass the barrier capacitance, and the diode will fail. The barrier capacitance of the switching diode is generally very small, which is equivalent to blocking the barrier capacitance and achieving the effect of good unidirectional conductivity under the condition of high frequency.