Oscillator using ad829 works - trying to make it work using 741

[Jony130]

Vo as 20 v I load as 4 A

I understand about the op amp now.

Sure I understand now, this driver needs a higher voltage, right?

But it's only rated for 20,

Ok I see, for such a large load current L1 value looks good.

As for the high side driver you can use this one.
http://www.avrfreaks.net/index.php?name=PNphpBB2&file=printview&t=128299&start=0

 

[FOIWATER]

I need a high input to turn on the mosfet. This seems like a different scenario, no?

I guess.. a high signal IS technically turning on the mosfet.. but it's a low signal from the driver which accomplishes it?

 

[Jony130]

This circuit will do the job

 

[FOIWATER]

I wouldn't feel right using it outright. But I will try my best to learn from it. Thanks, Jony

Do these circuits eliminate the need for a driver??

I am lost here

 

[Jony130]

Of course R1 represent the load resistance. And this circuit work exactly the same as this one
http://www.avrfreaks.net/index.php?name=PNphpBB2&file=printview&t=128299&start=0
The only difference is that the input is a emitter, and thanks to this high input will turn on the mosfet.

 

[FOIWATER]

How about if I use a separate supply for the driver and ground the source of the MOSFET.

If this will work, will 5 volts be enough?

 

[Jony130]

You want to use a floating power supply for a MOSFET ?

 

[FOIWATER]

for the driver, will that work?

 

[Jony130]

If you don't want to use this discrete MOSFET driver. I think you should try to use IR2011. You can power it from 12V power supply you already have in your design.

 

[FOIWATER]

Really.. but as you said, 12 volts to the gate of the MOSFET will not allow me to have 28 volts at the source?

I will have 12 - Vgs only, no?

I don't think I understand drivers

 

[Jony130]

But IR2011 has high side driver with external diode and capacitor. And this will boost the gate voltage up to
28V + 12V.

 

[FOIWATER]

I did not know this thanks Jony