Identification of Surface mount Transistor and Field Effect Transistor (MOS)

The transistor and field-effect transistor in digital electronic products are generally black, with most having three pins and a few having four pins (two pins in the transistor are connected, usually the emitter E or source S). There are also forms of dual transistor packaging and dual MOS transistor packaging. It should be noted that the shape and function of a transistor are very similar to those of a field-effect transistor, and it is difficult to distinguish them on a circuit board. Only by using schematic diagrams and printed circuit board diagrams can they be identified. When making judgments, attention should be paid to distinguishing them to avoid misjudgment. There are two types of transistors, NPN and PNP, and two types of field-effect transistors, NMOS and PMOS. Their gate G, source S, and drain D correspond to the base B, emitter E, and collector C of the transistor, respectively. However, compared to transistors, field-effect transistors have high input resistance and operate with almost no signal current at the gate, making them voltage controlled components.

Precautions for using MOS transistors: The input impedance of MOS transistors is high, so even small input currents can generate high voltages, causing the transistor to break down. Therefore, when disassembling the field-effect transistor, an anti-static soldering iron should be used, and it is best to use a hot air gun. In addition, the gate should not be suspended to prevent the discharge of gate charges and breakdown of the field-effect transistor.

There are also packaging methods such as double transistor and double field-effect transistor. There are two types of diodes that are simply packaged together, and there are also two diodes that have a logical relationship, such as forming an electronic switch.