The letters of the components in the circuit diagram indicate
The classification of item types is related to the classification of components, but they are not completely consistent. For example, ceramic capacitors and electrolytic capacitors, although the circuit symbols are different, the letters of their item types are all C. Transistor and MOS tube are also different kinds of devices, but the letters of their item types are all Q.
PS:
The letters of components such as resistors, capacitors, inductors, diodes, etc. are uniform in the electronics industry. However, some components, such as connectors, transistors, etc., may be represented by different letters in different companies. This book only introduces the more common letter representations. Of course, in the same company, the letter representation of the components must be uniform