Principle and application of triode
Triode principle
To understand the amplification function of triode, remember one thing: it will not produce energy for no reason, so triode will definitely not produce energy.
But the greatness of triode is that it can control large current through small current.
The principle of amplification is to control large static DC through small AC input.
Suppose the triode is a dam. The strange thing about this dam is that there are two valves, a big valve and a small valve. Small valves can be opened by manpower, while large valves are relatively heavy and cannot be opened by manpower, so they can only be opened by hydraulic power of small valves.
So the usual workflow is that whenever water is released, people will open a small valve and a stream will trickle out. This trickle will touch the switch of the big valve, and the big valve will open accordingly, and the turbulent river will flow down.
If the opening of a small valve changes constantly, so will the large valve. If it can be changed strictly in proportion, then perfect control is completed.
Here Ube is a small water flow, Uce is a large water flow, and people are input signals. Of course, if the proportion of water flow is current, it will be more accurate, because transistors are current control elements after all.
If one day, the weather is very dry and the river is gone, it is that the big water is empty there. At this time, the administrator opened the small valve. Although the small valve still hit the big valve as usual and left it open, there was no water flow, so there was no water flow. This is the cutoff region of the triode.
The saturated area is the same, because the river has reached a great level at this time, and the size of the valve opened by the administrator is useless. If the valve is not opened, the river will burst by itself, which is the breakdown of the diode.
In the analog circuit, the general valve is half-open, and the output water flow is determined by controlling its opening. When there is no signal, water will flow, so there will be power consumption when it is not working.
In the digital circuit, the valve is in the open or closed state. When not working, the valve is completely closed and does not consume electricity.
The metaphors about saturation zone and cutoff zone behind you are problematic, but you must know these principles, hehe.
To quote your metaphor, let me revise it:
Cut-off area: it should be that the opening of the small valve is not enough to open the valve. This situation belongs to the restricted area.
Saturation zone: The small valve should be opened too wide, so that the water discharged by the large valve can reach its limiting flux. But if you turn down the small valve, the transistor can return from the saturation region to the linear region.
Linear region: that is, the water flow is in an adjustable state.
Breakthrough area: For example, if there is water in a reservoir, the water level is too high (corresponding to high Vce), resulting in a gap and water flowing out. And with the opening of the small valve, the breakdown voltage becomes lower, which means it is easier to break down.
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Terminology description
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I. Triode
Triode is two PN junctions living on a piece of semiconductor material. Because each semiconductor transistor has two PN junctions, it is also called bipolar junction transistor.
A triode actually connects two diodes with the same electrode. It is a current control element. Using the special structure of narrow base region and the diffusion and recombination of carriers, the control of base current to collector current is realized, which makes the transistor have stronger control ability. According to the internal structure, triode can be divided into PNP tube and NPN tube, and the two tubes can be connected in a certain way to form a pair of tubes, which has stronger working ability. According to the power consumption of triode, it can be divided into low power triode, medium power triode and high power triode.
Second, the role and application
Triode has the function of amplifying current signal and switching control. Therefore, triode can be used to amplify signals and control the on-off of current. Transistors can be seen in power supply, signal processing and other places, and integrated circuits are also made up of many transistors connected in a certain circuit form, which has certain uses. Triode is the most important current amplifier.
Three. Important parameters of triode
1, β value
β value is the most important parameter of triode, because β value describes the amplification ability of triode to current signal. The higher the β value, the stronger the amplification ability of small signals, and vice versa; However, the β value cannot be made very large, because it is too large, and the performance of the transistor is unstable. Generally, the β value should be selected between 30 and 80. Generally speaking, the β value of triode is not a specific reference value, and generally changes slightly with the working state of the element.
2. Interelectrode reverse current
The smaller the reverse current between the electrodes, the higher the stability of the triode.
3, triode reverse breakdown characteristics:
The triode consists of two PN junctions. If the reverse voltage exceeds the rated value, it will be broken down like a diode, thus reducing performance or permanently damaging it.
4. Operating frequency
The β value of triode only remains unchanged within a certain working frequency range. If they exceed the frequency range, they will drop sharply with the increase of frequency.
Fourth, classification
According to different amplification principles, triodes can be divided into bipolar junction transistors (BJT) and unipolar transistors (MOS/MES type: metal oxide semiconductor or metal semiconductor). BJT has two kinds of carriers, but only one MOS carrier conducts electricity. BJT is generally a current control device, while MOS type is generally a voltage control device.
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