Class AB 25w MosFet Amp improved

166

01:58:52

This is an altered circuit that puts out 8w, I am working to increase the output.

published 9 years ago

rich11292000

9 years ago

Fets backwards, CFS

hurz

9 years ago

What is the 750 Ohm for at output? Will be impossible to make 25W at 758 Ohm with just 33V

Phildela

9 years ago

Rich, FETs backwards? Hurz, the resistor is in the original diagram, reducing or removing it puts heavy DC clipping on the output

hurz

9 years ago

Yes sure. But loudspeaker impedance is around 8Ohm and not 750Ohm. Do you think EC default FETs are good for an power amplifier? EC ones are more for IC opamp application for a few uA. You need to adapt them. Anyway, there is much more todo then just copying a schematic from net. Keep it up.

Phildela

9 years ago

Thank you Hurz for your useful comments, Ill look into these areas. I admit freely that I am a relative novice to Amplifier design and I am trying to learn about the different parts that make up design (eg LTP and biasing defining classes and active current loads). I will adjust some parameters and remove the 750 ohm to see if I can fix this circuit using real life parameters.

hurz

9 years ago

I don't recommend you to go to examples and start with Kirchhof's law etc. cuz i have the feeling you know most of it. Correct me if i'm wrong. However, i won't start with a full blown design. Start with parts of it like a push pull out stage, or simpler a emitter follower. Do some calculation about DC power at resistors. Etc..... Keep it up!

Phildela

9 years ago

I have been a service engineer for over 30 years, but have forgotten a lot. I know about a variety of components and know how to fault find various types of circuits by testing ICs and transistors. But my job does not call for actual design, and amplifiers are not my strong point as I work mostly in the digital area.

rich11292000

9 years ago

Mosfet fix: http://everycircuit.com/circuit/6133056069959680

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