From the output power point of view: The power amplifier emphasizes the power amplification of the signal, the load impedance is low, not only requires the voltage to be amplified, but also requires the output of sufficient output current. For example, TDA2030 mentioned upstairs, its voltage gain can be 40DB, current output can reach 4.5A. The operational amplifier mainly emphasizes the voltage amplification of the signal, the load impedance is generally higher, and the output current is smaller, generally not more than 100mA. From the perspective of signal amplification accuracy: The power amplifier accuracy is generally low, while the operational amplifier accuracy is high.
In fact, you are limited by textbooks and only learn other principles of a certain function, which is not related to a little reality.
In actual use, according to the purpose, the same (or similar) functions in the textbook are divided into different sayings.
For example, in the analog electronics, I have used a large length to discuss the triode, but it only said that the formula and the principle are not in contact with the actual book, and then the op amp. Finally, the power amplifier is also mentioned, but it is generally not required in schools.
"Amplifier" is relative to the purpose, but also relative to the load.
For example, a power amplifier must be used in the audio system. Why is the name of the power amplifier here, why is it used? It is only one reason, because the final sounding device-the speaker, what is the principle of the "speaker"? It is A device that needs a large current to push, for example, to exchange a few amperes of current to make it emit a loud sound. (I do n’t use any term here)
In order to meet the big stomach king of speakers, you can only make a circuit in front of it to provide a large current to make it pronounced. This circuit is a current amplifier, the formal name is called a power amplifier, or "power amplifier" for short.
In addition
Transformers for 220V to low voltage are just to provide a large current (power consumption is also considered, but not the most important).
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