Triode is one of the basic semiconductor components, which has the function of current amplification and is the core component of electronic circuits.The triode is to make two PN junctions close to each other on a semiconductor substrate. The two PN junctions divide the whole semiconductor into three parts. The middle part is the base area, and the two sides are the emission area and the collector area. The arrangement modes are PNP and NPN.
triode[1](Also called transistor) In Chinese, it is just a general term for three pin amplification devices. The transistor we often refer to may be several devices.
It can be seen that although they are all called triodes, in fact, there are many different expressions in English. The word triode is actually a unique pictographic word in Chinese.
Bipolar transistor[4]
"Triode" is the only English translation of "triode" in the English Chinese dictionary. It is related to the first appearance of the electronic triode, and it is the original object of the word "triode" in the true sense.Other devices called triodes in Chinese cannot be translated into Triode in actual translation.
Electronic triode (commonly known as TriodeElectronic tubeOne of)
metallic oxideFull English name of MOSFET (Metal Oxide Semi Conductor Field Effect Transistor)
VMOS (Vertical Metal Oxide Semiconductor)
Note: These three appear to be field effect transistors. In fact, metal oxide semiconductor field effect transistors and V-groove field effect transistors are unipolar structures, corresponding to bipolar structures, so they can also be collectively referred to asUnipolar transistor（Unipolar Junction Transistor）。
J-type field effect transistor is uninsulatedField effect transistorMOSFET and VMOS are insulated field effect transistors.
VMOS is a new type of power transistor with high current and high amplification (cross channel), which is improved on the basis of MOS. The difference is that the V-slot is used, which greatly improves the amplification factor and working current of MOS tubes, but also greatly increases the input capacitance of MOS tubes. VMOS is a high-power improved product of MOS tubes, but it has a huge difference from traditional MOS tubes in structure.VMOS has only enhanced MOS transistors, but not depletion MOS transistors.
Development history
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December 23, 1947, United StatesNew JerseyMurray MountainBell LaboratoriesThree scientists——BadinDr., Dr. Brighton, andShockleyThe doctor was carrying out the experiment nervously and methodically.They are experimenting with semiconductor crystals to amplify sound signals in conductor circuits.The three scientists were surprised to find that a small amount of current passing through one part of the device they invented could control a much larger current flowing through the other part, resulting in amplification effect.This device is an epoch-making achievement in the history of science and technology - transistor.Because it was invented on the eve of Christmas and has such a huge impact on people's future life, it is called "Christmas gift for the world".Therefore, the three scientists jointly won the prize of 1956The nobel prize in physics。
[2]New research found that depositing a layer of corresponding material outside the substrate at the electron outflow end of the transistor can form a semiconductor cooled P-N structure. Because the electronic energy level of N material is low and the electronic energy level of P material is high, when electrons flow through, they need to absorb heat from the substrate, which provides a good way for the heat dissipation of the crystal tube core.Because the heat taken away will be in direct proportion to the current, the industry also vividly calls this“Electronic blood”Heat dissipation technology.The new cooling triode is called N-PNP or NPN-P according to the polarity position of the new material added.
Transistors have brought about and promoted the "solid-state revolution", which in turn has promoted the semiconductor electronics industry worldwide.As a major component, it has been first applied in communication tools in a timely and universal manner, and has produced huge economic benefits.Because transistors have completely changed the structure of electronic circuits, integrated circuits andlarge-scale integrated circuitAs the times require, the manufacture of high-precision devices such as high-speed electronic computers has become a reality.
Crystal triode (hereinafter referred to as triode) can be divided into two types according to materials: germanium tube and silicon tube.Each one has NPN and PNP structures, but the most commonly used are silicon NPN and germanium PNP triodes (where N means negative charge in English),N-type semiconductors add phosphorus to high-purity silicon to replace some silicon atoms and generate free electron conduction under voltage stimulation, while P means positive charge, which means adding boron to replace silicon and generating a large number of holes to facilitate conduction.In addition to the different power supply polarity, the working principles of both are the same. The following only introduces the current amplification principle of NPN silicon tube.
Figure 1
For NPN tube, it is composed of two N-type semiconductors with a P-type semiconductor sandwiched between them. The PN junction formed between the emission area and the base area is called the emission junction, while the PN junction formed between the collector area and the base area is called the collector junction, and the three leads are calledEmitterE (Emitter), base b (Base) andcollectorc (Collector)。As shown in Figure 1
Schematic diagram of NPN transistor
When the potential of point b is a few volts higher than the potential of point e, the emitter junction is in a positive bias state, while when the potential of point C is a few volts higher than the potential of point b, the collector junction is in a reverse bias state, and the collector power supply Ec is higher than the base power supply Eb.
When manufacturing the triode, consciously make the concentration of most carriers in the emission region larger than that in the base region, and make the base region very thin. In addition, strictly control the impurity content, so that once the power is turned onEmission junctionPositive bias, most carriers (electrons) in the emission region and most carriers (holes) in the base region can easily diffuse across the emission junction to each other. However, because the concentration of the former is greater than that of the latter, the current passing through the emission junction is basically an electron flow, which is called the emitter electron flow.
Due to the thin base area and the reverse bias of the collector junction, most of the electrons injected into the base area cross the collector junction and enter the collector area to form the collector current Icn. Only a few (1-10%) of the electrons are recombined in the holes in the base area, and the recombined holes in the base area are resupplied by the base power supply Eb, thus forming the base current Ibn. According to the principle of current continuity
Ie=Ib+Ic
That is to say, by adding a small Ib to the base, a large Ic can be obtained on the collector, which is called current amplification. Ic and Ib maintain a certain proportion, namely:
β1=Ic/Ib
Where: β 1 - is called DC magnification,
The ratio of collector current change △ Ic to base current change △ Ib is:
β= △Ic/△Ib
In the formula, β is called ACCurrent magnificationBecause the values of β 1 and β at low frequency are not very different, sometimes for convenience, we do not strictly distinguish them, and the value of β is about tens to more than one hundred.
α 1=Ic/Ie (Ic and Ie are the current in the DC path)
In the formula, α 1 is also called DC amplification factor, which is generally used in common base configuration amplification circuit, and describes the relationship between emitter current and collector current.
α =△Ic/△Ie
α in the expression is the amplification factor of AC common base current.Similarly, the difference between α and α 1 at small signal input is also small.
The following relationship exists between the two amplification factors that describe the current relationship
The current amplification function of triode is actually to control the large change of collector current by using the small change of base current.[3]
Triode is a kind of current amplification device, but in actual use, the current amplification of the triode is often transformed into voltage amplification through resistance.
Amplification principle
1. The emitting region emits electrons to the base region
The power supply Ub is added to the emission junction through the resistance Rb, and the emission junction is positively biased. Most carriers (free electrons) in the emission region continuously cross the emission junction into the base region, forming the emitter current Ie.At the same time, most carriers in the base region also diffuse to the emission region. However, since the concentration of most carriers is far lower than that in the emission region, this current can be ignored, so it can be considered that the emission junction is mainly an electron current.
2. Diffusion and recombination of electrons in the base region
After entering the base area, the electrons are first concentrated near the emission junction, gradually forming the electron concentration difference. Under the effect of the concentration difference, the electron flow is promoted to diffuse to the collector junction in the base area, and is pulled into the collector area by the electric field of the collector junction to form the collector current Ic.There is also a small part of electrons (because the base region is very thin) recombination with the holes in the base region. The ratio of the diffuse electron flow to the composite electron flow determines the amplification ability of the triode.
3. Collecting area collects electrons
Because the reverse voltage applied to the collector junction is very large, the electric field force generated by this reverse voltage will prevent the electrons in the collector region from diffusing to the base region, and at the same time, the electrons diffused near the collector junction will be pulled into the collector region to form the main current Icn of the collector.In addition, a few carriers (holes) in the collector area will also drift, forming reverse saturation current flowing to the base area, which is represented by Icbo. Its value is very small, but it is extremely sensitive to temperature.
d. According to power: small power tube, medium power tube, high power tube
e. According to the operating frequency: low-frequency tube, high-frequency tube, and overfrequency tube
f. According to structural process: alloy pipe, plane pipe
g. According to the installation mode: plug-in triode, patch triode
Product parameters
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characteristic frequency
When f=fT, the triode completely loses the current amplification function.If the operating frequency is greater than fT, the circuit will not work properly.
FT is called gain bandwidth product, that is, fT=β fo.If the current triode operating frequency fo and high-frequency current magnification are known, the characteristic frequency fT can be obtained.As the operating frequency increases, the magnification will decrease. fT can also be defined as the frequency when β=1
Voltage and current
This parameter can be used to specify the voltage and current range of the tube.
hFE
Current magnification.
VCEO
Reverse breakdown voltage of collector emitter, indicating the saturation voltage at critical saturation.
PCM
Maximum allowable dissipated power.
Packaging form
Specify the appearance shape of the tube. If other parameters are correct, different packaging will result in the failure of the component to be implemented on the circuit board.
Judgment type
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Figure 3
Judging the pin position of the triode, the pin position of the triode has two packaging arrangements, as shown in Figure 3: the triode is a junction typeresistorThe three pins of the device have obvious resistance data. During the test (taking the digital multimeter as an example, red pen+, black pen -), we will switch the test gear to the diode gear (buzzer gear), as shown in Figure 4: the forward resistance of the base (B) of the normal NPN structure triode to the collector (C) and emitter (E) is 430 Ω - 680 Ω（This value is different according to different models and magnification）Infinite reverse resistance;The reverse resistance of the base (B) of the normal PNP triode to the collector (C) and emitter (E) is 430 Ω - 680 Ω, and the forward resistance is infinite.The resistance of collector C to emitter E is infinite without bias.The test resistance of base to collector is approximately equal to the test resistance of base to emitter. Generally, the test resistance of base to collector is 5-100 Ω less than the test resistance of base to emitter (the high-power tube is obvious). If it exceeds this value, the performance of this element has deteriorated, so please do not use it again.If misused in the circuit, it may cause the working point of the whole or part of the circuit to deteriorate, and the component may also be damaged soon. High power circuits and high-frequency circuits have obvious response to this poor component.
Figure 4
Although the package structure is different, it has the same function and performance as other types of tubes with the same parameters. Different package structures are only used for specific applications in circuit design.
It should be noted that some manufacturers produce some non-standard components, for example, the normal pin position of C945 is BCE, but the pin position arrangement of this component from some manufacturers is EBC, which will cause those careless workers to install new components into the circuit without detection, resulting in the circuit can not work, and in serious cases, the associated components, such as the switching power supply used on TV, will be burned.
Figure 5
In our commonly used multimeter, the test triode pin arrangement diagram (see Figure 5):
First, assume that one pole of the triode is the "base", connect the black probe to the assumed base, and then connect the red probe to the other two electrodes in turn. If the resistance measured twice is large (about several to dozens of K), or both are small (hundreds to several K), replace the probe to repeat the above measurement. If the two measured resistance values are opposite (both very small or both very large), it can be determined that the assumed base is correct.Otherwise, assume another pole is "base" and repeat the above test to determine the base.
When the base is determined, connect the black probe to the base and the red probe to the other two poles. If the measured resistance value is very small, the triode is NPN, otherwise it is PNP.
Determine collector C and emitter E, taking NPN as an example:
Connect the black probe to the assumed collector C, and the red probe to the assumed emitter E, hold the B and C poles with your hand, read the C and E resistance values shown on the meter head, and then connect the red and black probes in reverse to retest.If the resistance of the first time is smaller than that of the second time, the original hypothesis is valid.
structure type
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The crystal triode is to make two PN junctions close to each other on a semiconductor substrate. The two PN junctions divide the whole semiconductor into three parts, the middle part is the base area, and the two sides are the emission area and the collector area. The arrangement modes are PNP and NPN.
The corresponding electrodes are led out from the three regions, namely the base b emitter e and the collector c.
The PN junction between the transmitting region and the base region is called the transmitting junction, and the PN junction between the collecting region and the base region is called the collecting junction.The base region is very thin, while the emission region is thick, and the impurity concentration is high. The emission region of the PNP triode "emits" holes, whose moving direction is consistent with the current direction, so the emitter arrow is inward;The emission area of NPN type triode "emits" free electrons, which move in the opposite direction to the current, so the emitter arrow is outward.The emitter arrow is also the conduction direction of the PN junction under the forward voltage.Both silicon triodes and germanium triodes are PNP type and NPN type.
Packaging form and pin identification of triode
The commonly used triode packaging forms include metal packaging and plastic packaging, and the pin arrangement has certain rules,
The bottom view is placed so that the three pins form the vertex of the isosceles triangle, which is Ebc from left to right;For medium and small power plastic triode, make its plane face itself as shown in the figure, and place the three pins downward, then Ebc is from left to right.
There are many kinds of crystal triodes of various types in China, and the arrangement of pins is different. For the triode with uncertain pin arrangement in use, it is necessary to measure and determine the correct position of each pin, or look up the transistor manual to clarify the characteristics of the triode and the corresponding technical parameters and data.
Product function
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The crystal triode has the function of current amplification. Its essence is that the triode can control the large change of collector current with the small change of base current.This is the most basic and important characteristic of triode.We call the ratio of Δ Ic/Δ Ib the current magnification of the crystal triode, which is represented by the symbol "β".The current magnification is a fixed value for a certain triode, but it will change with the change of base current when the triode is working.
working condition
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Cut off status
When the voltage applied to the emitter junction of the triode is less than the conduction voltage of the PN junction, the base current is zero, and the collector current and emitter current are both zero. At this time, the triode loses its current amplification effect. The gap between the collector and emitter is equivalent to the switch off state. We call the triode in the off state.
Zoom in status
When the voltage applied to the emitter junction of the triode is greater than the conduction voltage of the PN junction and at a certain appropriate value, the emitter junction of the triode is biased forward and the collector junction is biased backward. At this time, the base current controls the collector current, making the triode have a current amplification effect. The current amplification factor β=Δ Ic/Δ Ib. At this time, the triode is in the amplification state.
Saturation conduction
When the voltage applied to the emitter junction of the triode is greater than the conduction voltage of the PN junction, and when the base current increases to a certain extent, the collector current no longer increases with the increase of the base current, but does not change much near a certain value. At this time, the triode loses the function of current amplification, and the voltage between the collector and emitter is very small,The connection between collector and emitter is equivalent to the on state of switch.This state of triode is called saturation conduction state.
The working state of the triode can be judged according to the potential of each electrode when the triode is working. Therefore, the electronic maintenance personnel often take a multi-purpose ammeter to measure the voltage of each pin of the triode during the maintenance process, so as to judge the working condition and working state of the triode.
Product identification
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Judgment of triode base: according to the structure diagram of triode, we know that the base of triode is the common pole of two PN junction in triode. Therefore, when judging the base of triode, just find out the common pole of two PN junction, that is, the base of triode.The specific method is to adjust the multi-purpose meter to the R × 1k gear of the resistance gear. First, place the red probe on one foot of the triode, and touch the other two feet of the triode with the black probe. If it is fully connected twice, the foot placed by the red probe is the base of the triode.If it is not found at one time, change the red stylus to the other foot of the triode and measure it twice again;If it is not found, change the red stylus again and test twice.If it is not found, put the black stylus on one foot of the triode and use the red stylus to test it twice to see if it is all connected. If it is not successful once, replace it again.You can always find the base after 12 times at most.
Discrimination of triode type: There are only two types of triode, namely PNP type and NPN type.When judging, just know whether the base is P type or N type.When using the R × 1k gear of the multipurpose meter, the black probe represents the positive pole of the power supply. If the black probe is connected to the base, it means that the base of the triode is P type, and the triode is NPN type.If the red probe is connected to the base, then the triode base is N type, and the triode is PNP type.
The identification of triode type and pin is a basic skill for beginners of electronic technology. In order to help readers quickly master the test method, the author summarizes four pithy formulas: "three reverses, find the base; PN junction, determine the tube type;Down arrow, large deflection;Don't be sure, move your mouth. "Let's explain it sentence by sentence.
1: Reverse three directions and find the base
As we all know, a triode is a semiconductor device containing two PN junctions.According to the different connection modes of the two PN junctions, the triodes can be divided into two different conductive types: NPN type and PNP type.
The ohm gear of the multimeter shall be used for testing the triode, and the R × 100 or R × 1k gear shall be selected.The equivalent circuit of the ohmic gear of the multimeter.The red probe is connected to the negative pole of the battery in the meter, and the black probe is connected to the positive pole of the battery in the meter.
Suppose we do not know whether the triode under test is NPN type or PNP type, nor can we tell which electrode each pin is.The first step of the test is to determine which pin is the base.At this time, we take any two electrodes (for example, the two electrodes are 1 and 2), measure its forward and reverse resistance with two multimeter probes upside down, and observe the deflection angle of the needle;Then, take two electrodes 1 and 3 and two electrodes 2 and 3, measure their forward and reverse resistance respectively, and observe the deflection angle of the meter needle.In these three inverted measurements, there must be two similar results: one is that the needle deflects more than the other;The remaining time must be that the deflection angle of the pointer before and after the reverse measurement is very small. This time, the unmeasured pin is the base we are looking for.
2: PN junction, fixed tube type
After finding the base of the triode, we can determine the conductive type of the tube according to the direction of the PN junction between the base and the other two electrodes.Contact the black probe of the multimeter with the base electrode and the red probe with any one of the other two electrodes. If the pointer of the multimeter has a large deflection angle, then the triode under test is NPN type tube;If the deflection angle of the indicator pointer is very small, the tube under test is PNP type.
3: Down arrow, large deflection
Find out the base b, which of the other two electrodes is the collector c, which is the emitter e?Then we can use measurementThrough currentICEO method determines collector c and emitter e.
(1) For NPN type triode, the measurement circuit of the through current.According to this principle, use the black and red probes of the multimeter to measure the positive and reverse resistance Rce and Rec between the two poles. Although the deflection angle of the multimeter pointer is very small in the two measurements, careful observation shows that there will always be a slightly larger deflection angle. At this time, the current flow must be: black probe → pole c → pole b → pole e → red probe,The current flow direction is exactly the same as the arrow direction in the triode symbol, so the black probe must be connected to collector c, and the red probe must be connected to emitter e.
(2) For the PNP type triode, the principle is also similar to the NPN type. The current flow direction must be: black probe → e pole → b pole → c pole → red probe. The current flow direction is also consistent with the arrow direction in the triode symbol. Therefore, the black probe must be connected to the emitter e, and the red probe must be connected to the collector c.
4: Can't measure, move your mouth
If during the measurement of "along the arrow, large deflection", it is difficult to distinguish between the two measured pointer deflections before and after the reversal, it is necessary to "move the mouth".The specific method is: in the two measurements of "along the arrow, large deflection", hold the junction between the two probes and the pins with two hands, hold the base electrode b with your mouth (or touch it with your tongue), and still use the discrimination method of "along the arrow, large deflection" to distinguish the open collector electrode c and emitter e.The human body plays the role of DC bias resistance in order to make the effect more obvious.
Amplification circuit
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Basic structure
The basic amplifying circuit is the most basic structure in the amplifying circuit, and it is the basic unit of the complex amplifying circuit.It uses the input current of bipolar semiconductor triode to control the output current, or the input voltage of field effect semiconductor triode to control the output current, so as to achieve signal amplification.The knowledge of basic amplification circuit in this chapter is an important basis for further learning of electronic technology.
The basic amplifying circuit generally refers to the amplifying circuit composed of a triode or field effect transistor.From the circuit point of view, the basic amplifier circuit can be regarded as a two port network.The role of amplification is reflected in the following aspects:
1. The amplification circuit mainly uses the control function of triode or field effect transistor to amplify weak signals. The output signal is amplified in the amplitude of voltage or current, and the energy of the output signal is strengthened.
2. The energy of the output signal is actually provided by the DC power supply, which is only controlled by the triode to convert it into signal energy and provide it to the load.
Circuit composition
The basic amplifying circuit of common radiation configuration is that the input signal is added between the base and emitter, and the coupling capacitors C1 and Ce are considered to be short circuited to the AC signal.The output signal is taken from the collector to the ground through couplingcapacitorC2 isolates the DC quantity and only adds the AC signal to the load resistance RL.In fact, the common emitter configuration of the amplification circuit means that the triode in the amplification circuit is a common emitter configuration.
When the input signal is zero, the DC power supply provides the triode with DC base current and DC collector current through each bias resistor, and forms a certain DC voltage between the three poles of the triode.Due to the DC isolation effect of the coupling capacitor, the DC voltage cannot reach the input and output ends of the amplification circuit.
When the input AC signal is added to the emitter junction of the triode through the coupling capacitors C1 and Ce, the voltage on the emitter junction becomes the superposition of AC and DC.The signal in the amplification circuit is complicated, and the symbols of each signal are specified as follows: due to the current amplification of the triode, the ic is dozens of times larger than the ib. Generally, as long as the circuit parameters are set properly, the output voltage can be many times higher than the input voltage.A part of the AC quantity in uCE reaches the load resistance through the coupling capacitor, forming the output voltage.Complete the amplification of the circuit.
It can be seen that the DC signal of the triode collector in the amplification circuit does not change with the input signal, but the AC signal changes with the input signal.During amplification, the collector AC signal is superimposed on the DC signalcouplingCapacitance, only AC signal is extracted from the output.Therefore, when analyzing the amplification circuit, the method of separating the AC and DC signals can be used, which can be divided into the DC path and the AC path for analysis.
Principle of composition
1. Ensure that the core device triode of the amplification circuit works in the amplification state, that is, there is appropriate bias.That is to say, the emitter junction is positively biased and the collector junction is inversely biased.
2. The input circuit shall be set so that the input signal is coupled to the input electrode of the triode to form a changing base current, thus generating the current control relationship of the triode and changing into the collector current.
3. The output circuit shall be set to ensure that the current signal amplified by the triode is transformed into the form of electricity required by the load (output voltage or output current).
Product symbol
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The middle horizontal line is the base B, the other diagonal line is the collector C, and the arrow is the emitter E.
triode
Product naming
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Naming method of domestic semiconductor models (from national standard GB249_74)
Naming method of domestic semiconductor models
Part I: Use Arabic numerals to indicate the number of device electrodes.
Part II: Use letters to indicate the material and polarity of devices.
Part III: Use Chinese phonetic alphabet to indicate device type.
Part IV: Use numbers to indicate device serial numbers.
Part V: Use Chinese phonetic alphabet to express specifications.
Part I
Part II
Part III
Symbol
significance
Symbol
significance
Symbol
significance
two
diode
A
N-type germanium material
P
Ordinary pipe
-
-
B
P-type germanium material
V
Microwave tube
-
-
C
N-type silicon material
W
Manostat
-
-
D
P-type silicon material
C
Parametric tube
three
triode
A
PNP type germanium material
Z
Rectifier tube
-
-
B
NPN type germanium material
L
Rectifier tube
-
-
C
PNP type silicon material
S
Tunnel pipe
-
-
D
NPN type silicon material
N
Damping tube
-
-
E
Compound material
U
Photoelectric device
-
-
-
-
K
Switch
-
-
-
-
X
Low frequency low-power transistor
-
-
-
-
G
High-frequency low-power tube
-
-
-
-
D
Low-frequency high-power tube
-
-
-
-
A
High frequency high power transistor
-
-
-
-
T
Semiconductor thyratron
-
-
-
-
Y
Bulk effect device
-
-
-
-
B
apd
-
-
-
-
J
Step recovery tube
-
-
-
-
CS
Field Effector
-
-
-
-
BY
Semiconductor special device
-
-
-
-
FH
Composite pipe
-
-
-
-
PIN
PIN tube
-
-
-
-
JG
Laser device
Model selection and replacement
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1. First, compare the parameters. If you don't know the parameters, you can search his specifications on the network first.
2. Know the parameters, especially BVCBO, BVCEO, BVEBO, HFE, ft, VCEsat parameters.Find similar products by comparing various parameters.Even if the parameters are known, it is hard to find them. Some books are out of date and no new products are collected.
In line package model Model polarity Ft VCEO Ic hfe paired model
9011 1T NPN 150MHz 18V 100mA 28~132
9012 2T PNP 150MHz 25V 500mA 64~144 9013
9013 J3 NPN
9014 J6 NPN 150MHz 18V 100mA 60~400 9015
9015 M6 PNP
9016 Y6 NPN 500MHz 20V 25mA 28~97
9018 J8 NPN 700MHZ 12V 100mA 28~72
S8050 J3Y NPN 100MHz 25V 1.5A 45~300 S8550
S8550 2TY PNP
8050 Y1 NPN 100MHz 25V 1A 85~300 8550
8550 Y2 PNP
2SA1015 BA PNP
2SC1815 HF NPN 80MHz 50V 150mA 70~700 1015
2SC945 CR NPN 250MHz 50V 100mA 200~600
2SA733 CS
MMBT3904 1AM NPN 300MHz 60V 100mA300@10mAthree thousand nine hundred and six
