the first picture is output of comparator(U4A)...it must be amplified by mosfets..and i need a small circuit between mosfets and comparator...

 

In the 2nd schematic you posted, it looks like you're trying to use an LM324. That will never work at 100kHz. They're limited to just a few kHz. You need a much faster opamp.[/quote]

you are right.. in this circuit carrier is 3 khz-3V and input signal(sinus) 100hz-2V ... i will use faster opamp in real project...i used it to try to drive mosfets...just help me to drive please..i can make rest of it...please..you will make me to graduate...

 

Where does the signal which will control the MOS come from?

 

it comes from output of the comparator opamp(U4A)

 

First, you need to use a P-channel MOS for M24 to make your life easier. Then you can use BJTs to drive the gates of the MOS arranged in a push-pull pair because the output of the op amp can't supply much current and the MOS will turn on quite slowly.

 

yes that's the point...i tried push pull but it didnt work...maybe i am doing something wrong...could u make it and post here...please...just push pull

 

Connect the source of the p-channel MOS to the positive side of the power supply and its drain to the drain of the n-channel MOS.

 

We can't see any details on the fuzzy JPG file type schematics that are covered with chicken-pox dots and that you posted over at ImageShack instead of attached here.

If the schematic was saved as a very clear GIF or PNG file type, if you turned off the dots and if you attached the schematic here then we would be able to help you.

 

Audioguru,

If you click on the picture in the attachment it will zoom in.

 

i did what you said and i guess i could drive mosfets...here the pictures...look at them..are they right? but i have a few question...in the last picture as you can see current of power supply is too large(103A)...how can i get it down..and i wanna use equal supplies...for example i used 15V for opamp and i have to use the same voltage for mosfets...can i do like that?

 

The oscillator in your simulation is not oscillating. So both Mosfets are turned on and are shorting the supply.

If the oscillator worked then it will drive the gate of each Mosfet to 40V which will blow up the Mosfets. their max gate voltage is only 20V.

EDIT:Also since the opamps have a 15V supply and the Mosfets have a 20V supply then the Mosfets will both always be turned on.

 

so the circuit is true or not? i can design it in another simu program..

what should i do...i wanna 5w output power....what should mosfets supply voltage and opamps supply voltage be? it is hard to understand by writing...please draw it...

 

Yes you can use the same power supply. Put a 1K resistor between the gate and source of each MOS. Disconnect the common connection between the MOS gates and between the BJTs emitters. Then connect the emitter of Q29 to the gate of M28 and the emitter of Q33 to the gate of M31.

 

i did it but i guess the output of mosfets is not true..here...

 

You have connected the 1K resistors between the gate and the drain. The correct is between the gate and the source.

 

Also, put the NMOS on the top and the PMOS at the bottom.

 

i cant do it man..dont u have any simu program...please draw the mosfets and transistor connection and put here...

 

Here it is.

 

thank you so much...i am trying it

 

so does it work? i mean could you make it works in your simu program?