which program do u use??becos it doesnt work in my program...mosfets dont amplify...

 

Here is the new one, i made a fault on the previous one.

 

thank you so much bro..you are the best...i will try it too tomorrow..it is so late here and have to go to bed...thanks for your helps...if it doesnt work too could you go on helping me?

 

Yes I can help you. Also, note that the part numbers of the transistors used in the circuit were arbitrary chosen.

 

I think the simple amplifier should be made like this:

 

oh man...you are really the best...i can drive mosfets now...thank you so much..you saved my life thank you thank you...thank both of you...you are so kind...i know there are still good people like you in the world...thank you again

 

now i have to calculate the output power for 5w...how can i calculate resitors in bjts(50ohm and 1 k)becos my output current is 1.42A..according to formula P=I*I*Rload=1.42*1.42*8=16.1W (hoparlor's resistor is 8 ohm) i need 790mA ouput current...aplifier works but i need 5w ouput power..it is the last step...thanks again..

 

The 50 ohms feeding 1k ohms does not attenuate the signal much. The value of 50 ohms might be much too high to quickly charge and discharge the high gate capacitance of the Mosfets, then they switch slowly and burn out. That is why I did not use the 1k and I used 10 ohms, not 50 ohms.

R81 does nothing except reduce the max output level. Remove it.

The frequency of the oscillator is only about 80Hz. The lousy old LM324 quad opamp can't go much higher.
The values of the lowpass filter reduce all frequencies above only 100Hz.
The inductor is huge.

If the Mosfets swing 21V p-p then the RMS power is 6.9W into 8 ohms. The resistance of the inductor of the lowpass filter will reduce the power a little or a lot.

EDIT: Math errors corrected

 

Here is the new one, i made a fault on the previous one.

i need to know how to calculate the resistors 1k and 500 ohm..could you help me mik?

 

The 1K resistor is used to limit the current through the base and its value depends on the gain of the transistors. A 1K will ensure that there is enough current through the base to drive the transistor into saturation.

The 50 ohm resistor prevents high currents to be developed through the BJT when the switching frequency is very high due to the capacitance of the MOS gate. To an approximation, just calculate it to limit the current below the transistors max limit if the MOS was a short circuit.