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Switching Characteristics Of Diode,What Is Diode Switch

Switching Characteristics Of Diode,What Is Diode Switch

September 25 , 2023 0

Switching diode is a semiconductor diode, is for the circuit "on" off "and special design and manufacture of diodes. It is from the conduction into the cut-off or from the cut-off into the conduction of the time required than the general diode is shorter than the common 2AK.2DK and other series, mainly used in electronic computers, pulse and switching circuits.

Switching Diode Principle

Semiconductor diode conduction is equivalent to a switch closure (circuit on), the cut-off is equivalent to a switch open (circuit cut-off), so the diode can be used as a switch, commonly used model 1N4148. due to the semiconductor diode has a unidirectional conductive properties in the positive bias under the PN junction conduction, in the conduction state of the resistance is very small, about tens of hundreds of ohms; in the reverse bias, it is a cut-off state, the resistance is very large. Very large, general silicon diode in more than 10MQ, germanium tube also has tens of kilo-ohms to hundreds of kilo-ohms. Using this - characteristics, the diode will play a role in the circuit to control the current on or off, becoming an ideal electronic switch The above description, in fact, applies to any ordinary diode, or diode itself is the principle. But for the switching diode, the most important feature is the performance under high frequency conditions.
At high frequencies, the barrier capacitance of the diode exhibits a very low impedance and is connected in parallel with the diode. When this barrier capacitance itself reaches a certain level of capacitance, the switching performance of the diode is seriously affected. Extreme conditions will short-circuit the diode high-frequency current no longer passes through the diode, but directly bypass the barrier capacitance through, the diode fails. Switching diode barrier capacitance is generally very small, which is equivalent to block the barrier capacitance of this road, to achieve the high frequency conditions can also maintain a good unidirectional conductivity effect!

Switching Diode Switching Methods

Ideally, a diode would be fully on (open) in forward direction and fully off (closed) in reverse direction, and the transition between on/off would be clean. But the reality of the diode is not so, for example, a major problem is that from forward to reverse, the diode can not be followed immediately by the conduction to cut-off, but to reverse after a small delay before turning to cut-off, during this time, the diode is first "reverse conduction", it is from the" reverse conduction" slowly. Reverse conduction" slowly turned to reverse cutoff. This is a problem in some circuits. In order for the circuit to work properly, it is required that the diode does not have this delay phenomenon. Through the improvement of the process and materials, made nearly ideal diode, this is the "switching" diode.

Switching Diode Characteristics

The characteristics of a switching diode include the following main points：

Switch-on time; the time taken from cut-off to switching on the switching diode is known as the switch-on time, the shorter this time is the better. Reverse recovery time; once the switching diode is activated then the forward voltage can be separated. The time it takes for the switching diode to switch off from conduction is called the reverse recovery time. Generally, this time is longer than the switch-on time.

Switching time, the switching time is the sum of the turn-on time and the reverse recovery time. Switching diodes switch fairly quickly. the reverse recovery time of Ge switching diodes is several hundred nanoseconds, while Si switching diodes are only a few nanoseconds. Once a forward voltage is supplied to the terminals of the switch, the switching diode is said to be in the on state, and is therefore equal to the on state of the switch. Similarly, when a reverse voltage is supplied to the diode, the diode is said to be in the off state, which is equal to the off state of the switch. Switching diodes utilise this key characteristic to obtain faster and better switching speed characteristics, smaller overall on-state internal resistance, higher disposable resistance and small junction capacitance of the PN junction.

Advantages Of Switching Diodes

The advantages of switching diodes include the following main elements
Fast switching speed
Small size
Long service life
High reliability
Better performance
Less noise
Fast recovery time
Ability to operate in harsh environments
Suitable for small signal switching up to 100mA