a. According to material: silicon tube, germanium tube
b. According to the structure: NPN, PNP. as shown in picture 2:
c. According to function: switch tube, power tube, Darlington tube, photosensitive tube, etc.
d. According to power: small power tube, medium power tube, high power tube
e. According to the working frequency: low frequency tube, high frequency tube, overclocking tube
f. According to the structure and technology: alloy tube, flat tube
g. According to the installation method: plug-in triode, patch triode