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Lets take a look on a linear amplifier
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Md Mubdiul Hasan:
Hi there,

Hope my post find you well.
I like to get attention the knowledgeble person in this post !
So, kindly avoid this post if you wont have experience.

I wanna post a circuit that may be explained by Dr. Kolar, a famous Swiss or Austrian proffesor.

I need to know this application well, because I want to develope a 3-phase-calibrator.
My application needs to amplify signal to a  certain level. Class D switching is necessary!

Here we go ....
Explain kindly

1. Why we need to think SNR for this case?
2. Why we need to think frequency gain voltage booster? Loop gain!
3. Explain impedences, transcondactance etc for whole circuit.
4. How the voltage and current is being controlled here?


Thanks a lot!

moffy:
This is just a very basic MOSFET output linear amplifier. No class D switching here. The tricky part is biasing the output FETs over temp to avoid:
1. Too much cross over distortion
2. Too much idle current.

You need to explain your end application better if you want help.
Md Mubdiul Hasan:
Dear Sir Moffy,

You could start with some information that is offcourse necessary at this moment.

In case of frequency domain, we cant see anything in feedback path of amplifier. Signal amplification  in both side is slightly  understandable.

I am thinking to use TIP142 , C1815, A1050, TIP147 for both current and voltage amplification. Like darlington pair, one transistors collector can be connected to others base.

As you said  distortion matters.
My application generates a lot of heat, because it 5 A application.





Benta:
Your schematic is a fairly classic symmetric linear audio power amplifier with MOSFET output stage. Most probably designed to run in Class B or AB mode.
I'd say, based on the supply voltages, that it's designed for around 200 W output power.

Nothing Class D about it, but you can of course feed it with a square wave signal if you like.

Power stage quiescent current is set with the "~10 V" voltage in the middle (which should be thermally coupled/compensated with the output MOSFETs).

I have no idea why you want to use such "whopper" transistors as the TIP142/147. All the MPSAxx types are small-signal and uncritical, The BF871/872 MOSFET drivers are CRT horizontal transistors and are high voltage and high frequency, which is needed in this circuit.


Md Mubdiul Hasan:
Thank you to take a part here.

My current design might be class AB then!! :palm:

Its feedback opamp is 551, input series RC element is 13k, 1uF.

Feedback parallel element may be 4.7 k, .33uF. Output has .33u and 10ohm series RC.

I am using TIP147, TIP142, C1815, A1015. They are properly biasd like cascaed 3 stage, may be AB class network. More symmetric way, like one pairs AB class output is connected to others pair. Last pairs base is connected to first pairs base! At last a voltage divider of 5 ohm has been made between 2nd and 3rd outputs!


Biasing voltage of this amplifier is plus, minus 24 volt.
The problem I am facing is heating !
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