Can someone explain this class A amplifier

The different classes may look like each other, for instance this can be also a class B amp or a class AB amp with only one slight modification. The only thing that separates them is the idle current drawn by the output transistors when no input is applied. In class A the output transistors must ideally draw 1/2 the maximum current of the load. For instance if your load draws 1A (pk-pk) the idle current must be set at least at 500mA. This way the output swings 500mA above the idle current and 500mA below the idle current. In reality this is quite unachievable. Even at best class A amps rarely reach this 50% efficiency, so most of the times the idle current is set at let's say 3/4 the load current. Output transformer coupled class A amps may have an efficiency close to 50%, but ideally never exactly or above 50%. This is the major disadvantage of class A amps, that they waste good amount of energy even when no signal or low level signal is applied. This can sometimes lead to efficiency levels of less than 10%, down to 0% when no signal is applied. A good class A amps are also more difficult to design than class B amps, because they need more aggressive temperature drift compensation feedback and a good thermal coupling of components, and also a good class A design is not a single ended one, but a push pull. That's because a single ended design is more prone to spurring even order harmonics, where in push pull designs, even order distortion usually gets cancelled

Thanks thebugger for the good info

Sorry buggzy. In best case a class A amp can have 25% efficiency. Only in theorie! But as long nobody running a class A amp from rail to rail voltage, the efficiency is much lower and about 10 to 20%

I just made a transformer coupled class A amp and it has 41% efficiency?

But the amp from AmpFan is transformerless. Later on you talked about transformers. But a pure class A can not have more then 25% efficiency. With transformer the theoretical max is 50% but even 40% is a little to realistic. Dont forget EC transformer primary resistance is 100mOhm fix even if inductivity is 50H!

Yes it's all theoretically. As I said in the comment there is no way to actually reach the 50% efficiency. There are some classes like Class H that bypass the rules slightly, but in reality it's pretty much impossible.

I have no idea

Guess there is more to learn

I get the classes and I know how they work but i don't get it's topology into the driver section. Thanks for the help I appreciate it a lot!

The driver section is exactly what determines the class. See if you drop more voltage across the transistors they'll conduct more, and sooner or later you'll push them in class A. The drop across them is usually handled by the driver section. I see the driver section with two separate applications. One handles the gain and distortion cancelling and the other handles the steady biasing of the output stage. They're usually intertwined, but have two distinct functions.

To really test it I will build it in real life and give you feedback.

Actually your bias is almost correctly set to work with an 4ohm load, but your output is no properly adjusted. It has some DC offset. To minimise the DC offset, you should keep the 200k resistor on the left, the same value as the 22k resistor on the right of the differential amplifier. Also you should add a potentiometer between the two emitters of the differential amplifier with the wiper connected to the constant current source. This way you can finely adjust the DC offset and also add some emitter degeneration which increases the stability.

@thebugger it is 22K in reality but i made it 200k so the simulation can run

@thebugger I set it at 22k and i added a potentiometer but it doesn't want to set i set it at 0V dc offset and restart the sim or it crashes or it sets itself to6-8V dc offset

I forgot to mention, that's a big value for the potentiometer. Use a 100ohm potentiometer. And don't simulate it. EC doesn't cope well with split rail power supplies and will often give you no solution. In reality it should work, although you can view some of my examples I've made a few low offset class A and class B amps here that should work super well in reality. Here's a link to one of mine hifi systems http://www.gadgetronicx.com/50w-hi-fi-audio-amplifier/

Wait you made this as like a project or you created this i've seen this amp allot in the past when i was 13. Looks preety cool let me guess LM3886

No, it's my design

so you made the amp Holly balls that's amazing!!!

Yeah I haven't made it in reality, but I believe to have compensated for a lot of the things that may happen.