(Sticker) transistor knowledge

Structure and type of Transistor  
Crystal transistor is one of the basic components of semiconductors and is the core component of electronic circuits. The transistor is made on a semiconductor substrate to form two close Pn knot, two The PN junction divides the positive semiconductor into three parts. The middle part is the base zone, and the two parts are the emission zone and the Collector zone. PNP and Two kinds of, the corresponding electrode is derived from three zones, respectively, as the baseline B release pole E and collector C.  
Between the launch zone and the base Zone The Pn knot is called the launch knot. The PN junction is called the collector. The base area is very thin, and the emission area is thick and the impurity concentration is large, PNP transistor launch zone "Launch "The hole moves in the same direction as the current, so the emission pole arrow is inside; Transistor launch zone "Launch "It is a free electron, and its movement direction is opposite to the current direction, so the emission pole arrow is outward. The emission pole arrow is outward. The arrow pointing to the pole is also The conduction direction of the PN Junction Under the forward voltage. Both silicon transistor and Ge transistor PNP type and Type.  
Encapsulation form and pin identification of Transistor  
Commonly used transistor packages include metal packages and plastic packages, and the pin arrangement has certain rules. For small-power metal transistor packages, they are placed at the bottom view position shown in the figure below, make the Three pins form the top of the isosceles triangle, from left to right E B C; for small and medium power plastic transistor, the plane is directed to itself according to the figure, and the three pins are placed downward, then from left to right E B C.  
At present, there are many types of transistor in China, and the pins are arranged in different ways. in use, the transistor with uncertain pin arrangement must be measured to determine the correct position of each pin, or find the transistor User Manual to clarify the characteristics of the transistor and the corresponding technical parameters and materials.  
Current amplification of Transistor  
The crystal transistor is capable of current amplification. the essence is that the transistor can control the large variation of the collector current with a small amount of base current. This is the most basic and important feature of a transistor. We will The ratio of △ic to △ib is called the current magnification of the transistor. "β" indicates. The current magnification is a fixed value for a single transistor, but the baseline current changes as the transistor works.  
Three operating states of Transistor  
Cutoff status: when the voltage added to the transistor junction is less The conduction voltage of the PN junction, the base current is zero, and the collector current and the emission current are both zero. The transistor loses the current amplification function, and the switch is disconnected between the collector and the emission pole, we call the transistor in the cutoff state.  
Amplification status: when the voltage added to the transistor junction is greater When the conduction voltage of the PN junction is at an appropriate value, the forward offset of the transistor transmitting junction and the reverse offset of the collector junction. At this time, the base current controls the collector current, enables current amplification of the transistor. β = Delta IC/Delta IB, then the transistor is enlarged.  
Saturated conduction status: when the voltage added to the transistor junction is greater When the base current increases to a certain extent, the collector current does not increase with the base current increasing, but does not change very much near a certain value, at this time, the transistor loses the current amplification function. The voltage between the collector and the emission pole is very small, and the conduction state between the collector and the emission pole is equivalent to the switch. This state of the transistor is called the saturated conduction state.  
　　 The working status of the transistor can be determined based on the potential of each electrode during the operation of the transistor. Therefore, during the maintenance process, the electronic maintenance personnel often need to use an electric meter to measure the voltage of each foot of the transistor, determine the operating status and status of the transistor.  
Use multi-purpose electric meter to detect Transistor  
Differentiation of the Transistor Base pole: according to the structure of the transistor, we know that the base pole of the transistor is two of the three The public pole of the PN junction. Therefore, when determining the basis pole of the transistor, you only need to find two The public pole of the PN junction, that is, the base pole of the transistor. The specific method is to adjust the multi-purpose electric meter to the power blocking R×1k block, first put a red table pen on one foot of the transistor, and use a black table pen to touch the other two feet of the transistor, the foot of the red table pen is the base pole of the transistor. If not, the red table pen is switched to the other foot of the transistor and tested twice. If not, the red table pen is changed and tested twice. If not, place the black table pen on the foot of the transistor and use the red table pen to test whether the table is completely connected twice. In this way, no quantity is allowed at most. 12 times, you can always find the base pole.  
Identify the transistor type: There are only two types of transistor, namely, PNP and PNP. When determining, you only need to know that the base pole is a P-type material and n-type material. Multi-purpose electric meters When the r × 1k block is used, the black table Pen represents the positive pole of the power supply. If the black table pen is turned on when the base pole is connected, it indicates that the base material of the transistor is very p type, and the transistor is type. If the red table pen is connected to the base pole for conduction, it indicates that the Transistor Base is very n type material, and the transistor is PNP type.