Triode, the full name should be semiconductor triode, also known as bipolar transistor, crystal triode, is a semiconductor device that controls the current. Its role is to amplify the weak signal into a larger amplitude electrical signal, and is also used as a contactless switch. There are seven common categories.

1. Material division
    According to the material division, the triode can be divided into two kinds of silicon tube triode and germanium tube triode.

2. Divide according to structure
    According to the structure, the triode can be divided into NPN type triode and PNP type triode.

3. Divide according to function
    According to the functional division, the transistor can be divided into switching tube, power tube, Darlington tube, photosensitive tube and so on.

4, according to the power division

    According to the power division, the triode can be divided into small power tube, medium power tube and high power tube.

5, according to the working frequency
    According to the operating frequency, the triode can be divided into three types: low frequency tube, high frequency tube and overfrequency tube.

6, according to the structure of the process
    According to the structure and process, the triode can be divided into alloy tube and flat tube.

7, according to the installation method
    According to the installation method, the triode is divided into plug-in triode and patch triode.