SMT patch proofing diodes are also called transistors, which are important components in electronic circuits. Its main function is current amplification and switching.
Types of diodes:
There are many types of SMT chip proofing diodes, which can be divided into germanium tubes and silicon tubes according to their usage. If divided by purpose, it can be divided into ordinary diodes and special diodes. Common diodes include detection diodes, switching diodes, and Zener diodes; special diodes include varactor diodes, photodiodes, light-emitting diodes, and so on. The commonly used diodes in the circuit are introduced as follows:
a. Rectifier diode.
The diode that rectifies alternating current into direct current is called a rectifier diode. Rectifier diodes are mostly made of silicon semiconductors, and use the unidirectional conductivity of the PN junction to convert AC into pulsed DC, that is, rectification.
b. Detector diode.
The detector diode can detect the low-frequency signal modulated on the high-frequency electromagnetic wave. It has high detection efficiency and good high-frequency characteristics.
c. Zener diode.
Zener diodes use the principle that the voltage at both ends of the diode does not change when the diode is reversed to achieve voltage limiter and overload protection. It is widely used in regulated power supply devices.
d. Switching diodes.
Switching diodes use the unidirectional conductivity of the diode with small resistance when forward biased and large resistance when reverse biased to control the current in the circuit and play the role of switching on or off.
e. Varactor diode.
SMT patch proofing varactor diodes use the characteristic that the PN junction capacitance changes with the magnitude of the reverse voltage applied to the tube to replace the variable capacitance in circuits such as tuning.
f. Light-emitting diodes.
When the forward voltage of the light-emitting diode is 1.5-3V, it can emit light as long as the forward current passes. Light-emitting diodes are mainly used to indicate the role of display, which can be composed of LED digital tubes of numbers or symbols.
The photodiode converts photoelectric information into electrical signals. When there is light, its reverse current increases proportionally with the increase of light intensity. It is used for light measurement or as an energy source, that is, photocells.
h. Fast recovery diode.
SMT patch proofing fast recovery diode is a kind of semiconductor diode with good switching characteristics and short reverse recovery time. It is mainly used in switching power supplies and PWM pulse width.
Used as high-frequency rectifier diodes, freewheeling diodes or damping diodes in electronic circuits such as modulators and frequency converters.
2. Classification of transistors:
There are many types of triodes, and the specific classifications are as follows.
a. According to the manufacturing materials, it can be divided into silicon triode and germanium triode.
b. If divided according to the conductivity type, it can be divided into PNP
Type and NPN type. Among them, germanium transistors are mostly PNP type, and silicon transistors are mostly NPN type.
c. If divided according to the working frequency, it can be divided into low frequency tube and high frequency tube. Generally, the working frequency of the low-frequency tube is below 3MHZ, and the working frequency of the high-frequency tube can reach several hundred MHZ.
d. If divided according to the allowable power dissipation, it can be divided into small power tube and high power tube. Generally, the rated power consumption of a small power tube is below 1W, while the rated power consumption of a high-power tube is above several tens of watts.