Small Audio Amplifier

Since this is a sinusoidal wave, you can use Vo/✓2 for Vrms and do similar calculations for Irms and Prms (Prms is Po/2 though)

And i doesn't look like you need that 470u after the op amp

The cap is needed. It helps with the distortion and a faster ON time.

It may lower the output but it removes other problems, so in my opinion, 0.3 dB is worth being lost to remove problems like distortion and power being drawn from the Op Amp.

I don't know a lot about opamps so why can't the 470 be removed and the output cap be increased and fix the same issues?

For several reasons, the main one is to not have any power going from or into the op amp. Second is for a better audio quality, which the cap removes distortion. Third, because I am not going to use electrolytic caps because they are polarized and would explode and create a short circuit. And also, the final cap just allows for lower frequencies to sound just as good, aswell as power the negative half of the sine wave.

Thank you for that info

Remove the 470uF, use global feedback from the load (change the 10k to 8k2), and then you can remove the 5k and 100k input biasing.

@GROGOR Sorry, I'm not going to do that. First of all, your idea wont work unless the powersupply has a negative voltage, which I do not own neither I have seen. Second, the output is lowered for all that.

Not true, sshsslfun. I made this a few weeks back. It works. It's not perfect but it works despite the cap, and positive and negative rail. http://everycircuit.com/circuit/6376918768418816

@sshsslfun, i wish you are more going into detail, you are to quickly in your conclusion. reading your profile give a clear overview you think everything is toooo easy. I wish you listen a little more and to really understand amplifier and oscillators and OpAmps it needs much more then a few days! Some do not understand all after even 20years and we have many users here who will never understand, i dont expect that valid for you but anyway even you will need a bit more then a few days

P = (Vp/sqrt (2))*(Ip/sqrt (2)) = (Vp*Ip)/2 to answer your question in the circuit description @sshsslfun

I calculated an output wattage of 9.4W, an input wattage of 27W, a power dissipation of 15.6W, and an efficiency of 35%.

@PrathikP @crake Thanks for the link and the formulas! @jason9 Thanks, I want to use this circuit and improve it.

@sshsslfun, what i was saying is, listen to @GROGOR more closely and dont judge to quickly as you have learned "ALL" about amplifiers,oscillators and OpAmps just in september? Funny. Two times 100 Ohm and two diodes as VAS at 30V is quite a high current which will cause quite a high quiet sense current (in EC default saturation of diode is identical to base emitter diode) ! But the output power transistor does not look like power transistors, they look like simple TO92 package BC547. OpAmps do deliver standard 20mA and not hundreds of mA specialy not at 30V cuz they are made like AB amplifier and do have also a power dissipation. The capacitor is not needed if set the operating point to supply/2 15V which suppose to be also at input the operating DC voltage. So you need a symetric voltage divider and not this asymetric thing you have now. One tip, start at loudspeaker and try to simulate what you really have in your toolbox and build it step by step from right to left, form loudspeaker to the input amplifier.

http://everycircuit.com/circuit/5411165642686464

No negative rail needed.. Global feed back utilised instead of just local on your op amp, and removed all that wasted current through those diodes!

hmmm, make the loop so big and even include the coupling output capacitor is not a good idea, i wont take it inside the loop. Check the example from @crake which is best, even the output stage power transistors are much to weak.

Why not good? They improve overall performance of whole cct..

Redesign and split your power supply. http://everycircuit.com/circuit/5411165642686464

@sshsslfun im not teasing you or anything, but how do you know how op amps work but dont know the most basic formulaes?

GROGOR I cannot open your links for some reason

@PrathikP, guess you are on a black list of sshsslfun he will not communicate with people who are talking against his ideas! 😀 tip: this will work as long you go in kindetgarten but it diesn't if you growup running away or ignoring is not a solution of a problem. @sshsslfun think about

btw, @jason9 you also need to learn some new strategies!

http://everycircuit.com/circuit/5664050196512768

Crake. Try that.. Just some experimenting.. Cct got bridging a quad h-class amp.

Haha @hurz Nah I have no black list, I have not been able to be on EC. Ive been very busy recently and I cant read everything. I do not know how they work, I just know basic functions like comparators and setting up their gain. I ask for the formulas because on a previous circuit , I calculated the wrong outputs with that same formulas, but I went back to that circuit, and realized that I missed some info that hurz gave to me, it was about calculating the sine wave's RMS power along with DC power, since the sine wave had DC current. I cant read every comment right now, but Ill try to during the weekend, thank you all for your comments and your help along with your attention.

It was the attention that i wanted, the circuit just an excuse.. Lolola

@hurz, what new strategies? I’d like to learn them.

Stratedgy of a wonderful 13 year old, whom isn't 13 any more,,! Perhaps!?!

here we are again http://everycircuit.com/circuit/4611152047505408