Audio amplifier basics

Learn more about our portfolio of audio amplifiers

In this video, we will discuss the basic purpose of audio amplifiers. We will
cover the basic function of transistors and some of the key specifications to
consider when selecting an audio amplifier. Then, we will take a brief look
at the common amplifier topologies: Class-A, Class-B, Class-AB and Class-D.

[swrekcfest]

Thanks ! Nice to see information here about amplifiers from a reputable source !

[gkdresden]

Relating the efficiency one should preferably discuss the theoretical upper limit in order to determine what a practical realization reaches compared to it. One should also mention, that the minimum efficiency is always zero, independently of the amplifier class used. The maximum efficiency of an realized amplifier always relates to its maximum output power for a specified THD+N. In the typical use of an amplifier the efficiency is always much lower than this maximum efficiency.

If you have a class AB audio amplifier with a maximum output power of 100 Wrms at home it is often operated at a typical output power of 1 W or even lower. So it is not surprizing that the efficiency under this condition is only a few percent. Often its idle current is higher than the current to drive the speaker.

The theoretical limit of a class A amplifier depends on its output stage design. If you use a emitter follower operating against a current sink its maximum efficiency is 25% because the current sink has to consume the the maximum speaker current. If you operate a push pull output stage the idle current needs to be only half of the maximum speaker current. So the maximum efficiency is 50%.

The maximum efficiency of a class B amplifier is 78.5% for rail to rail operation. This is also the maximum efficiency of a class AB amplifier in the limit of an idle current of zero. For a finite idle current its efficiency is always lower than 78.5%.

The maximum efficiency of a class D amplifier is 100%. For very high output power in the order of 1 kW or more you can also come very close to it. But if you have a low power class D amplifier providing just 100 to 1000 mW allready its preamplification stage and its analog to pwm converter can greatly reduce the efficiency to just 50 to 70%.

[altuber_athlete]

Excellent explanation! Why I didn’t in school I understood in this video.

[chamindasilva]

The Class A amplifiers without negative feedback(without an emitter resistor):poor d.c stability and suitable for small signal amplifications such as R.F and I.F amplifiers, etc.
The Class A amplifiers with negative feedback(with an emitter resistor):good d.c stability, low distortion(T.H.D), it is suitable for large signal amplifications(normally voltage amplification).
The class A amplifiers are not suitable for power amplifications.

[alexandrulazar]

Hello man, i need to chose a amp for my sub, if the amp it with 2 channel s and it says 180rms that mean for each channel or in total? Sorry for my bad english

[DREAMCATCHER-ejns]

I need to make 2.1 amplifier, can you suggest a best audio ic

[Nathanael.Thomas]

Is this just a plug for TI's smart amps? Seems like less of a category of amplifier and more like a product. Good information otherwise!

[CooperHerb]

Bruh I didn't understand a word this dude said, what courses should i study to build up to this?

[stopfoolingpeople]

Wanted to learn! And you ran like a wild horse! You need to speak slow to allow newbies grasp!

[tertia]

PCM & DSP in audio electronics is so much snoofery.

[montasirelkhair]

He is probably reading from a book this is not basicccc