The transistors and FETs in digital electronic products

The transistors and FETs in digital electronic products are also generally black, most of which are three pins, and a few of which are four pins (there are two pins in the transistor, generally emitter E or source S). It is also available in dual transistor packages and dual MOS transistor packages. It should be noted that the shape and function of the transistor is very similar to the FET, and it is difficult to distinguish on the circuit board, only with the help of schematic diagram and printed board diagram recognition, judgment should pay attention to distinguish, so as not to misjudge. There are two types of transistors, NPN and PNP, and field effect transistors have NMOS s and PMOS s, and their gate G, source S, and drain D correspond to the base B, emitter E, and collector C of the triode, respectively. However, compared with transistors, FETs have a high input resistance, and the gate hardly takes signal current when operating, so it is a voltage control element.

Precautions for the use of MOS : The input impedance of MOS  is high, so that a small input current will generate a high voltage and make the  breakdown. Therefore, when disassembling the FET, an anti-static electric soldering iron should be used, and it is better to use a heat gun. In addition, the gate cannot be suspended, so as to avoid the gate charge being released nowhere and breaking down the FET.