Audio Amplifier. Which class should I use?

[Shayaan_Mustafa]

Oh. Great.

Thank you very much. Now I can recognize which is LPF and which HPF. It is great. :-D

I want to thank you a lot. You are my real teacher.

 

[goldsmith]

Thank you very much. Now I can recognize which is LPF and which HPF. It is great.

Congratulations !

I want to thank you a lot. You are my real teacher.

Just a friend ! :-D

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By the way can you ask my question in post 401 ? if yes we can continue !

 

[Shayaan_Mustafa]

You said in post#354 to place the passive network in between load and MOSFET. Here you are using this passive network at output. So we are taking output at inductor. Is it cause of the problem?

 

[goldsmith]

No it is not a problem !
Let me change my question ! are you familiar with Lenz law really ?

 

[Shayaan_Mustafa]

Yes I am familiar. So current direction will change?

 

[goldsmith]

Not just that ! VL=-L*(di/dt ) . L is large and dt is low and di is pretty high . then you will have a minus voltage across the DS junction but with pretty high value . what should you we do to protect our mosfet from explosion !!!! ?

 

[Shayaan_Mustafa]

It is all related to the direction of the current or change in magnetic flux.

 

[goldsmith]

Read post #407 , again , please .

 

[Shayaan_Mustafa]

I think we can use a high value resistor. As voltage with high value will mostly drop across it. What can be the other choice rather than a resistor...

 

[goldsmith]

no if the resistor be high , the problem will be available too . and we don't want use low value resistor because we don't want loss the energy !

 

[Shayaan_Mustafa]

OK. Let me think again.

We must prevent voltage to increase oppositely to the developed polarity on the MOSFET. Right.

 

[goldsmith]

Right ! it is enough that you just consider this problem when occurs that the mosfet is turned off !

 

[Shayaan_Mustafa]

So if MOSFET is turned off then the opposite polarity voltage will not be able to destroy it?

May be I am wrong or what do you mean by above statement?

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Sir I have to go now. But you post what you want to say. I will see it in morning.

Good morning.

 

[goldsmith]

if that minus voltage was low there won't any problem but because there isn't any path , for inductor it can exceed from some KV !!!! can you predict what will happen ? nothing special , but you just made a hand made bomb instead of SMPS !!!!!!!

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Good morning shayaan . see good dreams !

 

[Shayaan_Mustafa]

So I can make bomb with this one too... lol. hehehehehe....

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Electronics also help in making bomb. oh ..

So What can we do to prevent voltage increament?

 

[goldsmith]

A diode ! can you think about it ?

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Electronics also help in making bomb. oh ..

We shouldn't use knowledge in wrong path ! each thing that can suffer the other humans is in wrong path !

 

[Shayaan_Mustafa]

Hello sir!

A diode ! can you think about it ?

No. I can't think about a diode.
I have to clear now some thing about diode as high voltage protection.
First, let say at diode's anode we have -ve high voltage. Then it will be in cutoff. But if the voltages are too high then it can also be destroyed. Right?
Secondly, let say at diode's cathode we have -ve high voltage. Then it will hold just 0.7V across it and turns on (act like a short circuit if neglect bulk resistance). But due to high voltage it will allow to pass current and hence other components can get destroyed. Right?

I hope you are getting what I am trying to say. Please clear these question sir. If both above situations are correct then how can a diode prevent so high voltages?

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We shouldn't use knowledge in wrong path ! each thing that can suffer the other humans is in wrong path !

I was just wonder that electronic allows these devastating things too. I afraid if this great stuff would be hold in bad minds.

Really I want to serve mankind and want to be able electronic engineer like you. You are great.

 

[goldsmith]

Hi again , dear shayaan.
See below , please . what you understand from this circuit ? tell me that :


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By the way , i'm not an engineer , yet !

 

[Shayaan_Mustafa]

I understand this.

When MOSFET is on then diode has no current in it. so it has no voltage drop.

When MOSFET is off then diode has forward current through it and it has 0.7V across it. Right?

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If you are not an engineer yet. Then what are you doing as you are teaching me how to make an amplifier also SMPS.

I want to know about your qualification.

 

[goldsmith]

That is right . now another thing ! did you understand what happened ? the inductor , recharged the capacitor , when mosfet is off ! it prevented from damages and then recovered the energy into the capacitor !

And about your question about me ! i'm a student of university , and i have learned all of things that i know with myself and with reading gang of books and asked from many of my friends entire of the world . i told we are the same . the university didn't do anything for us , hence some years ago i understood i should learn myself ! now i'm giving my experiences to you . and nothing else !

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I'm working here , in my country as a freelancer . thus i have earned many experiences .