AB outputstage

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hi ...

i am studying electronics and have been given the objective by my lector, to design am amplifier with an class AB output stage to give about 150W at 8 ohm, with a quiescent current of 50 mA.

I want to use a Vbe multiplier and because of my output transistors i need a Vbb of at least 2.8V

so how should i do that... i just cant figure it out...

i thought i came to a solution with R2 = 3.3K, R1= 1k, and Iref = 2.5 but something is wrong... the Quiescent current i not at all 50mA... !!

What am i doing wrong ?
 
Four diodes (or diode strapped transistors) in series?
Laugh, but its the same parts count as the resistors....

Or you can diode strap ONE mosfet gate to drain,
and VGS-On might have about the right voltage.
But MOSFET temperature coefficient may bend
the wrong way for this application.

Maybe there is an LED with your voltage?
 
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