MOSFET RF power amplifier design

[spacecase0]

do you have a good RF resistor that is 50 ohms and can deal with the appropriate amount of power ?
if so, connect it, look at voltage and calculate from there
if trying to buy that resistor, most people call them a "dummy load"

[Buddhafollower]

You know, i do not have a Bird or a Daiwa or another RF power meter. How can i measure RF power using the oscilloscope?

[spacecase0]

I will get to it,
just busy lately

[Buddhafollower]

If you still can, then please continue to send me the book.
Thank you for what you have done for me so far.
May God be praised.

[spacecase0]

the reason you need the feedback at all is that transistors have higher gain when they heat up,
so as they run they get warmer, then they pull more current heating up even faster,
this is called thermal runaway. and it can fry transistors
(edit: if you control the input power while watching your output power you can avoid this happening without any feedback in the circuit)

page 96 of the book I have been sending you has the feedback circuit you are asking about
it is missing the capacitor that you have in series, but all that does is to stop the feedback from working on any DC current,
you have another system for biasing the transistor, so you don't want DC feedback anyway.

[Buddhafollower]

This looks good but for a given pair of transistors i don't know how to calculate the feedback network.

[spacecase0]

as far as your figuring out the transformers,
remember that the number of turns ratio is the same as the voltage ratio
so, some messy math later you get that the turns ratio squared equals the impedance ratio

as a check on that as well as being an example,
I am going to pick a 1:2 turns ratio transformer,
in 10V at 1A (10 ohms)
out should be 20V at 0.5A (40 ohms)
so 40/10 is ratio of 4 times the ohms out as in
the other way is 2 squared / 1 squared and that is 4
that ratio will work for any voltage you choose to do that math on.

as far as how many turns the primary should have,
the turns times the amps on the input is what matters,
you want to use much of the magnetic capability of the core, to few turns and your coupling is poor,
to many turns and you saturate the core and you get harmonics out and less power.
so go for something like 80% the saturation, but that is just a number I remember seeing somewhere, so I am not sure about it,
but you sure don't want something like 5% or 15% or 95% or 110%, (although 95% would be your best choice if you were forced to choose one of the 4 listed)
you want something high middle, and make sure you calculate peak power and not RMS (RMS times the square root of 2 gets you peak, so RMS times ~1.41 = peak)
hopefully that helps,

[spacecase0]

harmonics are often caused by clipping,
or at least something is not linear.
you could be overloading the ferrite, once you saturate the core it will start creating harmonics.
remember that you have the energy out of the amplifier, and it needs to go somewhere, it will bounce back into the system if it has no where to go.

out of time, will reply more later

[Buddhafollower]

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[Buddhafollower]

Truly humanity is far gone. Gone berserk or even worse
For the sake of conversation i will tell you that today morning i was on the internet on YouTube and there was an advertising from a doctor and ex-researcher, because he was fired of course, about the research that he and others have done concerning type 2 diabetes. The doctor looked like a good man and very well-intentioned and a real expert in what he was doing. So it seemed to me at least. He looked like a man with a deep longing for normality and love for humanity. He has a product named Sugar Balance. It is 100% natural, being made out of plants. The result comes in a few days or even after the first day. So he said. I myself trust him with my life. I don't have diabetes but i do trust him. Like him there are many naturopaths in US. My heart goes out to all of these poor people who are trying their best to improve things and to save people from their sufferings. I find myself sometimes crying inside because i see the hopelessness of our situation. I know some Science and i know some secrets, medical and technological as well. This man is now hunted down by pharmacological companies and allopathic giants, just because he dared speak against the system who wants the destruction of life on Earth. There are so many like him in USA... i feel so sorry for this society has so many geniuses that deserve a better life and real respect. On YouTube there is a ND named Peter Glidden. He is a very courageous genius of the medical world. I don't know what to say anymore. The suffering, ridiculous suffering, that humans create for themselves speaks for itself. They will do with Mr. David Pearson's cure just what they did with Laetrile/Amygdalin and Krebiozen and so many other miraculous drugs of natural origin, while all kinds of diseases sky rocket. I truly wonder what some beings gain out of all this pure hatred? Are they even normal? Certainly not.... This mess that the nowadays world is in certainly makes you think. So much hatred for life, for God's creation, so much insanity...
https://43d897265kne3ed0qv2ecjw2-wpe...W-20210126.jpg

Order out of Chaos.

[Buddhafollower]

By far the best material is 43. I will but from Mouser but right now my debit card expired apparently for.... no reason and i haven't got enough money to buy the amount i want. Maybe in a few months. For now i will use this material from Kemet. Anyway, there is no need for a better material for me. 10MHz are more than enough for my projects.
Say, can you teach me how to calculate the input and output impedance of a power transistor such as this 2SC3264 as an example so i will be able to calculate the signal transformers?
I really need this. Through trial and error i estimated the best number of turns for the power transformer to be 3 turns. There the sine wave seems better looking than with any other ratio. Again, is 1:3 turns.
At the input i have 4:2 with center tap at the secondary for biasing the two transistors.
I really need to know how to design the transformers and the amplifier in general, because the sine wave doesn't look too great at 1MHz and not so good at 2MHz either. Seems a bit bend to the right. This means some harmonics are present. It is very interesting how out of nothing, energy/information appears. Those harmonics truly appear out of nothing. I inject a perfect sine wave and the result at the other end is a distorted wave form. It is truly fascinating. I wish i had the knowledge in my hands so i could study this phenomenon. This truly takes a lifetime but on the way you are bound to discover things that open gates for energy to enter our world from Counterspace. Praised be Allah alone for It's many miracles.

[spacecase0]

reading the information on the core, I bet that is limiting your frequency,
I hope your tests work, but I am guessing you have to change your core
also, make sure to calculate your magnetic amount so you don't saturate the core

other cores
https://www.fair-rite.com/product-ca...nents/toroids/

[Buddhafollower]

It is an interesting material. The ferrite core is called ESD-R-25 for 10MHz from Kemet.
It may be because of this limitation, however, when i was setting the idle current to be very high, 600mA probably or even higher, the amplifier could go further in frequency without the sine wave being distorted too much. This is as far as i remember. I will try to set the current again using resistors smaller than 10kOhm and see what i will get except for the heat sink heating up excessively.

https://www.tme.eu/Document/54bb3e85...5001_ESD-R.pdf

[spacecase0]

what is your ferrite material ?
it might be one meant for low frequency only

[Buddhafollower]

I returned to thank you again for your kindness. It isn't a small thing to find someone that can help me and has the patience to do it.
May Allah help us all.