The triode is a great invention

Triode can realize such control , When there is no current at the base , It's cut-off , And when the base has a current , The triode turns on , This is a great invention , Because of this invention , Let Shockley and other three physicists get 1956 Nobel lecture in .

Next, briefly explain why it can achieve such a function , This is a NPN Structural diagram of the U-tube , that NPN What is it about ？ Let's start with the atomic structure , The outermost layer of a silicon atom has four electrons , Pure silicon crystals do not conduct electricity , Because silicon atoms and silicon atoms are together , The outermost layer can form a stable eight electron structure .

In this way, it is not easy for silicon atoms to get electrons , It is not easy to lose electrons , So pure silicon crystals do not conduct electricity , To make silicon conductive , People doped it , A phosphorus atom has five electrons in its outermost layer , We add phosphorus atoms to silicon atoms , At this time, there is an extra electron in its outermost layer , This electron needs only a little energy , Can become a free electron .

Recently, many little friends asked me for some MCU learning materials , Then I based on my ten years of experience , How many nights did you stay up , Carefully organize a 「 MCU introduction to advanced tutorial + tool kit 」, All free sharing to everyone ！！！

Comment area reply 666 , After paying attention to me, I can take the private message .

Back to the topic

Because free electrons are negatively charged , So call it N Type semiconductor ,N Taken from the negative The first letter of , In the same way , We doped boron atoms , So the outermost layer of the boron atom is missing an electron , Replace the missing cushion with a hole to attract electrons to show positive electricity , Let's call it alpha P Shape semiconductor ,P word positive The first letter of .

For the sake of understanding , hold P The type and N Type semiconductors are bonded together , It forms a diode , Power it up , There is an electric field , The direction of the force on the electron is opposite to the direction of the electric field line , Let's just throw away the electric field lines , It's easier to understand , When P When terminating the positive pole , The direction of the force is like this , Free electrons can move to the left , Compound with holes , Under the action of power supply , This kind of movement keeps going , This creates an electric current .

When N When terminating the positive pole , The direction of the force is like this , The free electron is forced by an electric field to the right , Cannot compound with holes , here PN The end of the knot , No current is generated , This is the unidirectional conductivity of the diode , The triode can be imagined as a pair of diodes P Zone interconnection .

These are its three zones , But doping is different from diode , Its emission region has the highest doping concentration , The doping concentration in the base region is very low , And it's very thin , When we are connected to the power supply , Triode cut off , When our power supply is reversed , The triode is still off , Why is that ？

We've already said that , Triode can be regarded as two diodes P Area connection , You see, the two diodes are in opposite directions , So whatever we do , There is a diode cut-off , In order to make this triode turn on , We give BE The stage is also connected to the power supply , At this time, the second stage tube begins to conduct , Free electrons in the emission region flow continuously to the base region , However, the hole concentration in the base region is very low , And it's very thin .

The base region cannot absorb so many electrons in a short time , Only a few electrons and holes combine to form a base current , The second part is attracted to the pole region , Form collector current , That is, the output current of the triode , The greater the current flowing through the base , There are more free electrons in the channel , Corresponding , More free electrons flow to the collector , This is the general principle of triode small current controlling large current .

The article is relatively long , More words , You can first open the avatar and pay attention to me , Then take your time ,/// Insert a ： At the beginning of this year, I recorded a set of systematic introductory single chip microcomputer tutorial , If you want, just ask me for it. It's free , I can send a private message ~ Click the black font in the lower left corner of my avatar and I can also get it . I've been relatively idle recently , Take me to finish the design , Take students to provincial or above competitions ///

The base area is made very thin to make it easier for electrons in the emission area to enter the collector area , The concentration is very low in order to form a smaller base current , In this way, more free electrons can flow to the collector , If the concentration is very high , It will be easy for free electrons to enter the base , In this way, less electrons will flow into the collector area , Because the number of electrons flowing out of the emission area is certain .

More electrons flow to the base , Then there will be less flow to the collector area , The doping concentration in the emission region is high , To ensure that there are enough free electrons entering the base region and the collector region , One last question for you , Can two diodes be welded together to form a triode ？ You can talk about your views in the comment area .

Okay , That's all for this issue , If you think it's helpful to you in front of the screen, please press one button three times