Read the triode easily. It turns out that it works like this

One ： Introduction of triode

triode , That is, semiconductor triode , It is a semiconductor device that controls the current , Its function is to amplify weak signals into electrical signals with large amplitude , Also used for contactless switches . Usually , Triode has the function of current amplification , Its structure is to make two closely spaced on a semiconductor substrate PN junction , Two PN The junction divides the whole semiconductor into three parts , In the middle is the base area , The two measuring parts are the transmitting area and the collecting area , Usually there are PNP and NPN Two kinds of .

  Two of the triode PN junction , Similar to two diodes with common negative or positive

Two ： Three working states of triode

Cut off status : The voltage of triode emitter junction is less than PN Junction conduction voltage , The base current is zero , Both collector current and emitter current are zero , The triode loses its current amplification function , Between the collector and the emitter is equivalent to the off state of the switch , We call the triode in the cut-off state .

Zoom in : When the voltage applied to the triode emitter junction is greater than PN Junction conduction voltage , The emitter junction of the triode is forward biased , Collector reverse bias , At this time, the base current controls the collector current , Make the triode have the function of current amplification .

Saturated conduction state : When the voltage applied to the triode emitter junction is greater than PN Junction conduction voltage , And when the base current increases to a certain degree , The collector current no longer increases with the increase of the base current , But in some - There is little change near the fixed value , At this time, the triode loses its current amplification function , The voltage between collector and emitter is very small , The conduction state between collector and emitter is equivalent to that of switch . This state of triode is called saturation conduction state .

3、 ... and ： The function of triode

· Amplify weak signals ： A small signal input from the base will lead to | Great current changes from collector , This is the most important and core part of electronic circuit .

· Used as a contactless switch ： Use the cut-off and conduction characteristics of triode to control or drive the load ; For example, the gate circuit composed of triodes 、 Switching power supply, etc .

Four ： Types of triodes

There are many kinds of triodes , According to different categories, there can be ：

① Semiconductor materials ： There are silicon tubes and germanium tubes ;

② according to Working frequency Come to share ： There are low-frequency tubes and high-frequency tubes ;

③ Divide according to power ： There are small power tubes , Medium power tube and high power tube ;

④ Press According to the function ： It is divided into switch tube , Power tube , Darlington tube , Photosensitive tube, etc .

We usually have NPN Type owner E Pole tube yes : 8050、 9013、 9014、 9018、 C1815、 D882、TIP41、 3DD15、 2N3055、 2N3773 etc. ;

common PNP Type a triode has : 8550、9012、 9015、 B772、 TIP42、 2N5884 etc. .

among , image 8050、8550、 9013、 9012 Such as this TO-92 Packaged E The pole tube belongs to the small power three = A polar tube ：

 

D882、B772、TIP41、TIP42 It belongs to medium power triode ：

3DD15、2N3055、2N3773、2N5884 Such a gold sealed iron cap triode belongs to a high-power triode ：

The above are all in-line triodes , Now there is this kind of SOT-23 Encapsulated patch Transistor ：

 

Four ： Important parameters of triode

1、β value ：

β Value is the most important parameter of triode , Because the value describes the amplification ability of the triode to the current signal .β The higher the value , The stronger the amplification ability of small signals , vice versa ; But the value can't be very big , Because it's too big , The performance of triode is not very stable , Usually, the value should be 30 to 80 It is advisable to .- In general , The value of the triode is not a specific value , It generally changes slightly with the working state of components .

2、 Reverse current between poles ：

The smaller the reverse current between poles , The higher the stability of the triode .

3、 Reverse breakdown characteristics of triode :

The triode consists of two PN Composed of , If the reverse voltage exceeds the rated value , It will be like two  _ A polar tube Be punctured like that , Degrade performance or permanently damage .

4、 Working frequency ：

The value of the triode remains unchanged only within a certain operating frequency range , If the frequency range is exceeded , They will drop sharply with the increase of frequency .

What is a triode ？ What is the classification and working principle of triode ？